Name: cooling an optically trapped ultracold fermi gas by periodical driving
Uploaded: 2017-03-30T14:00:00.000+00:00
Duration: 11 min 21 s
Description: Watch this Scientific Journal Video about Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving at JoVE.com

We thank Ji Liu and Wen Xu for involving in the experimental setup. Le Luo is a member of the Indiana University Center for Spacetime Symmetries (IUCSS). This work was supported by IUPUI and IUCRG.

<ol>
	<li>Petrich, W., Anderson, M. H., Ensher, J. R., Cornell, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable,+tightly+confining+magnetic+trap+for+evaporative+cooling+of+neutral+atoms.">Stable, tightly confining magnetic trap for evaporative cooling of neutral atoms.</a> Phys. Rev. Lett. 74 (17), 3352 (1995).</li><li>Ketterle, W., Druten, N. J. V., Bederson, B., Walther, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaporative+cooling+of+trapped+atoms.">Evaporative cooling of trapped atoms.</a> Advances in Atomic, Molecular, and Optical Physics. 37, 181-236 (2003).</li><li>Truscott, A. G., Strecker, K. E., McAlexander, W. I., Partridge, G. B., Hulet, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Observation+of+Fermi+pressure+in+a+gas+of+trapped+atoms.">Observation of Fermi pressure in a gas of trapped atoms.</a> Science. 291 (5513), 2570-2572 (2001).</li><li>DeMarco, B., Jin, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Onset+of+Fermi+degeneracy+in+a+trapped+atomic+gas.">Onset of Fermi degeneracy in a trapped atomic gas.</a> Science. 285 (5434), 1703-1706 (1999).</li><li>Granade, S. R., Gehm, M. E., O'Hara, K. M., Thomas, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=All-optical+production+of+a+degenerate+Fermi+gas.">All-optical production of a degenerate Fermi gas.</a> Phys. Rev. Lett. 88 (12), 120405 (2002).</li><li>Luo, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaporative+cooling+of+unitary+Fermi+gas+mixtures+in+optical+traps.">Evaporative cooling of unitary Fermi gas mixtures in optical traps.</a> New J. Phys. 8 (9), 213 (2006).</li><li>Li, J., Liu, J., Xu, W., de Melo, L., Luo, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parametric+cooling+of+a+degenerate+Fermi+gas+in+an+optical+trap.">Parametric cooling of a degenerate Fermi gas in an optical trap.</a> Phys. Rev. A. 93 (4), 041401 (2016).</li><li>Poli, N., Brecha, R. J., Roati, G., Modugno, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cooling+atoms+in+an+optical+trap+by+selective+parametric+excitation.">Cooling atoms in an optical trap by selective parametric excitation.</a> Phys. Rev. A. 65 (2), 021401 (2002).</li><li>Kumakura, M., Shirahata, Y., Takasu, Y., Takahashi, Y., Yabuzaki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shaking-induced+cooling+of+cold+atoms+in+a+magnetic+trap.">Shaking-induced cooling of cold atoms in a magnetic trap.</a> Phys. Rev. A. 68 (2), 021401 (2003).</li><li>Li, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sub-megahertz+frequency+stabilization+of+a+diode+laser+by+digital+laser+current+modulation.">Sub-megahertz frequency stabilization of a diode laser by digital laser current modulation.</a> Appl. Opt. 54 (13), 3913-3917 (2015).</li><li>Hamamatsu Photonics Deutschland GmbH. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> HiPic user manual. , (2016).</li><li>Luo, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Entropy and superfluid critical parameters of a strongly interacting Fermi gas [Ph.D. thesis]. , (2008).</li><li>Ries, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> A magneto-optical trap for the preparation of a three-component Fermi gas in an optical lattice [Diploma thesis]. , (2010).</li><li>Bartenstein, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precise+determination+of+6Li+cold+collision+parameters+by+radio-frequency+spectroscopy+on+weakly+bound+molecules.">Precise determination of 6Li cold collision parameters by radio-frequency spectroscopy on weakly bound molecules.</a> Phys. Rev. Lett. 94 (10), 103201 (2005).</li><li>Gaunt, A. L., Schmidutz, T. F., Gotlibovych, I., Smith, R. P., Hadzibabic, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bose-Einstein+condensation+of+atoms+in+a+uniform+potential.">Bose-Einstein condensation of atoms in a uniform potential.</a> Phys. Rev. Lett. 110 (20), 200406 (2013).</li><li>Bruce, G. D., Bromley, S. L., Smirne, G., Torralbo-Campo, L., Cassettari, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Holographic+power-law+traps+for+the+efficient+production+of+Bose-Einstein+condensates.">Holographic power-law traps for the efficient production of Bose-Einstein condensates.</a> Phys. Rev. A. 84 (5), 053410 (2011).</li><li>Roy, R., Green, A., Bowler, R., Gupta, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+cooling+to+quantum+degeneracy+in+dynamically+shaped+atom+traps.">Rapid cooling to quantum degeneracy in dynamically shaped atom traps.</a> Phys. Rev. A. 93 (4), 043403 (2016).</li><li>Bukov, M., D'Alessio, L., Polkovnikov, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Universal+high-frequency+behavior+of+periodically+driven+systems:+from+dynamical+stabilization+to+Floquet+engineering.">Universal high-frequency behavior of periodically driven systems: from dynamical stabilization to Floquet engineering.</a> Adv. Phys. 64 (2), 139-226 (2015).</li></ol>

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Presentiamo un protocollo sperimentale per il raffreddamento di un parametrica non interagente Fermi gas in una trappola ottica attraversato fascio. Le fasi critiche di questo protocollo includono: In primo luogo, il gas di Fermi otticamente intrappolati deve essere raffreddato vicino alla temperatura degenerato abbassando la profondità trappola. Secondo, una frequenza di modulazione è scelto che è risonante con il componente anarmonico del potenziale intrappolamento. In terzo luogo, l&#39;intensità del fascio di intrappolamento viene modulata per raffreddare la nuvola atomica e misurare la dipendenza dell&#39;energia nube sul tempo modulazione. Rispetto allo schema trappola-abbassamento, il regime di raffreddamento parametrico fornisce un modo selettivo per rimuovere atomi alta energia dalla trappola ottica senza abbassare la profondità trappola. Contribuisce ad aumentare la densità di fase e raffreddare un gas di Fermi non interagente. Poiché tale raffreddamento parametrica è solitamente anisotropa, ma fornisce anche un metodo conveniente per modificare anisotropia temperatura del gas quantisticoes. Per consentire il raffreddamento parametrico, l&#39;attuale protocollo richiede un gas di Fermi vicina alla temperatura degenerata come punto di partenza. L&#39;effetto di raffreddamento è limitata alla direzione assiale del potenziale intrappolamento. Queste due limitazioni sono causate dalla anarmonicità finita del ODT-attraversato fascio che è fatto da raggi laser gaussiane nel protocollo corrente. Per estendere questo metodo per diverse specie atomiche e applicarlo per grande campo di temperatura, è necessario aumentare l&#39;anarmonicità del potenziale intrappolamento. Proponiamo due miglioramenti per questa tecnica di raffreddamento. In primo luogo, il raffreddamento parametrica può essere implementato con un potenziale intrappolamento con grande anarmonicità nelle tre direzioni, quali la scatola trappole 15 o legge di potenza trappole 16, che ha il potenziale per raffreddare direttamente gli atomi intrappolati dallo stato termico nel regime degenere senza richiedendo abbassando la trappola otticotutti. In secondo luogo, agitando periodicamente il potenziale intrappolamento ottico attraverso un AOM 17, possiamo sintetizzare il trappola ottica con grande anarmonicità utilizzando il metodo Floquet 18.

Negli ultimi due decenni, varie tecniche di raffreddamento sono state sviluppate per la generazione di condensati di Bose-Einstein (BEC) e degenerare gas di Fermi (DFG) da vapori atomici caldi 1, 2, 3, 4, 5. BEC e DFG sono nuove fasi della materia che esistono in temperature estremamente basse, solitamente un milionesimo di grado sopra lo zero assoluto, nettamente inferiori a quelli normalmente presenti sulla Terra o nello spazio. Per ottenere tali temperature basse, la maggior parte dei metodi di raffreddamento si basano sulla riduzione del potenziale intrappolamento per raffreddare gli atomi per evaporazione. Tuttavia, lo schema abbassamento diminuisce anche il tasso di collisione degli atomi, che limita l&#39;efficienza di raffreddamento quando il gas raggiunge il regime quantistico 6. In questo articolo, presentiamo un metodo &quot;espulsione&quot; raffreddare per evaporazione un gas ultrafreddi Fermi in un colpo ODTabbassando la profondità trappola. Questo metodo si basa sulla nostra recente studio parametrico di raffreddamento 7, che mostra diversi vantaggi rispetto ai regimi abbassamento 7, 8, 9. L&#39;idea chiave dello schema parametrica è di impiegare l&#39;anarmonicità del ODT-attraversato fascio, che rende gli atomi caldi vicino al bordo del potenziale intrappolamento sentono le frequenze di cattura non inferiore ai atomi freddi del centro. Questo permette anarmonicità gli atomi caldi per essere selettivamente espulsi dalla trappola modulando il potenziale intrappolamento a frequenze risonanti con gli atomi ad alta energia. Il protocollo sperimentale di raffreddamento parametrica richiede un gas pre-raffreddato non interagenti Fermi vicino alla temperatura degenerata. Per implementare questo protocollo, un modulatore acusto-ottico (AOM) è utilizzato per modulare l&#39;intensità dei fasci di cattura di controlling modulazione di frequenza, profondità e tempo. Per verificare l&#39;effetto di raffreddamento, la nube atomico sia rilevato l&#39;imaging assorbimento di tempo di volo (TOF), in cui un fascio laser risonante illumina la nube atomica e l&#39;ombra assorbimento viene catturata da un dispositivo ad accoppiamento di carica (CCD). Le proprietà cloud, come il numero di atomi, energia e temperatura, sono determinati dalla densità colonna. Per caratterizzare l&#39;effetto di raffreddamento, si misura la dipendenza delle energie nube sulle varie volte modulazione.

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cooling an optically trapped ultracold fermi gas by periodical driving

We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs the anharmonicity of the ODT, in which the hotter atoms at the edge of the trap feel the anharmonic components of the trapping potential, while the colder atoms in the center of the trap feel the harmonic one. By modulating the trap depth with frequencies that are resonant with the anharmonic components, we selectively excite the hotter atoms out of the trap while keeping the colder atoms in the trap, generating parametric cooling. This experimental protocol starts with a magneto-optical trap (MOT) that is loaded by a Zeeman slower. The precooled atoms in the MOT are then transferred to an ODT, and a bias magnetic field is applied to create an interacting Fermi gas. We then lower the trapping potential to prepare a cold Fermi gas near the degenerate temperature. After that, we sweep the magnetic field to the noninteracting regime of the Fermi gas, in which the parametric cooling can be manifested by modulating the intensity of the optical trapping beams. We find that the parametric cooling effect strongly depends on the modulation frequencies and amplitudes. With the optimized frequency and amplitude, we measure the dependence of the cloud energy on the modulation time. We observe that the cloud energy is changed in an anisotropic way, where the energy of the axial direction is significantly reduced by parametric driving. The cooling effect is limited to the axial direction because the dominant anharmonicity of the crossed-beam ODT is along the axial direction. Finally, we propose to extend this protocol for the trapping potentials of large anharmonicity in all directions, which provides a promising scheme for cooling quantum gases using external driving.

Usando questo protocollo, si studia la dipendenza del raffreddamento parametrico sul tempo modulazione con la frequenza di modulazione di ampiezza e ottimizzato, entrambi i quali sono stati determinati nella precedente pubblicazione 7. Abbiamo dapprima una non interagenti gas di Fermi di 6 atomi di litio nei due bassi stati iperfini con una temperatura di T / T F ≈ 1.2. Qui, T F = (6N) 1/3 ħ ω / k B = 5.2 μK viene determinata con numero di atomi di N = 1,7 × 10 5 per giro e la media geometrica ω frequenza intrappolamento = (ω ω x y z ω) 1 / 3 = 2π × (2250 × 2450 × 220) 1/3 Hz, h è la costante di Planck ridotta, e k B è la costante di Boltzmann. Il tempo-Risultati dipendenti sono mostrati in figura 9 con frequenza di modulazione di 1.45ω x, e la profondità di modulazione di 0,5. Le immagini assorbimento TOF delle nubi atomiche (Figura 9a) mostrano una significativa riduzione delle dimensioni nube assiale con l&#39;aumentare del tempo di modulazione, indicativo della temperatura assoluta è continuamente ridotto di raffreddamento parametrica. Per descrivere quantitativamente l&#39;effetto di raffreddamento, usiamo E (x, z) / E F come termometria efficace per gas ultrafreddi Fermi 7, dove E f è l&#39;energia di Fermi ed E (x, z) sono le energie nube atomici del radiale e le direzioni assiali, rispettivamente. Abbiamo innanzitutto estrarre il numero formato indipendente quadratico medio (NIMS) dalla nube atomica. Poi dal NIMS, calcoliamo E (x, z) / E F di figura 9b. Dopo circa 500 ms modulazione, la E z / E F si riduce significativamente da 1.80 a 0,90 x E / E F è leggermente leggermente aumentata da 1.20 a 1.25. I numeri atomici decreasing in Figura 9b inserto indicano atomi vengono espulsi dalla trappola. Troviamo che il raffreddamento parametrico cambia l&#39;energia nube atomica in modo anisotropo, in cui l&#39;energia nella direzione assiale è inferiore alla energia di Fermi mentre quella radiale è ancora sopra l&#39;energia di Fermi. Si deve notare che le energie disuguali iniziali nella direzione assiale e radiale (figura 9b) è generato dalla trappola rapido abbassamento applicato nella sezione 6.3. Dopo il raffreddamento parametrico, l&#39;energia direzione assiale è notevolmente ridotta mentre l&#39;energia radiale è appena cambiata. Questo risultato indica il modo che il raffreddamento parametrico cambia la nube di energia è anisotropa. Questo effetto anisotropo è dovuto al fatto che ilanarmonicità dominante del ODT-attraversato fascio è lungo la direzione assiale 7. Tali campioni termodinamicamente anisotropi possono essere utilizzati per studiare processi termalizzazione in un sistema quantistico molti corpi interagenti. <img alt="Figura 1" src="/files/ftp_upload/55409/55409fig1.jpg" /> Figura 1: Sistema di ultra alto vuoto. La camera a vuoto dell&#39;apparecchiatura atomo ultrafreddo a IUPUI. 1. forno, 2. rallentatore zeeman, 3. bobine magnetiche, 4. camera esperimento e 5. telecamera CCD. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55409/55409fig1large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> <img alt="figura 2" src="/files/ftp_upload/55409/55409fig2.jpg" /> Figura 2: Modalità di funzionamento per il raffreddamento parametrica. La curva nera è la tempistica potenza laser in fibra. La curva rossa è uno otemporizzazione f ODT AOM. La curva ciano rappresenta il campo magnetico. La curva arancione è impulsi di imaging TOF. L&#39;asse orizzontale mostra la scala temporale di ogni fase. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55409/55409fig2large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> <img alt="Figura 3" src="/files/ftp_upload/55409/55409fig3.jpg" /> Figura 3: Livelli atomici 6 Li e frequenza del laser di bloccaggio spettri. a) 6 Li D 2 transizione per le travi di raffreddamento e repumping del MOT. b) La curva gialla è lo spettro di assorbimento saturo privo Doppler del 6 Li D 2 riga e la curva rossa è il relativo segnale di errore lock-in. Il picco sinistra è il 2 2 S 1/2 (F = 3/2) → 2 2 P 3/2 transizione, la destra è il 22 S 1/2 (F = 1/2) → 2 2 P 3/2 transizione, e quello centrale è il segnale d&#39;incrocio di due transizioni. La croce precipitare è il punto di bloccaggio. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55409/55409fig3large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> <img alt="Figura 4" src="/files/ftp_upload/55409/55409fig4.jpg" /> Figura 4: 6 Li forno. Ogni sezione etichettata contiene una bobina di riscaldamento a temperatura controllata per il forno di uscita del flusso atomico richiesto. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55409/55409fig4large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> <img alt="Figura 5" src="/files/ftp_upload/55409/55409fig5.jpg" /> Figu<html> Re 5: Zeeman più lento. La bobina crossover è l&#39;ultima sezione del Zeeman più lento. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55409/55409fig5large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> <img alt="Figura 6" src="/files/ftp_upload/55409/55409fig6.jpg" /> Figura 6: schema ottico MOT. La configurazione ottica per la generazione del MOT e raggi laser rallentamento. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55409/55409fig6large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> <img alt="Figura 7" src="/files/ftp_upload/55409/55409fig7.jpg" /> Figura 7: MOT ed immagini assorbimento ODT. a) un&#39;immagine MOT dopo la fase di pompaggio. b) L&#39;immagine del MOT sovrapposta e ODT._upload / 55409 / 55409fig7large.jpg&quot; target = &#39;_ blank&#39;&gt; Clicca qui per vedere una versione più grande di questa figura. <img alt="Figura 8" src="/files/ftp_upload/55409/55409fig8.jpg" /> Figura 8: sbarrato fascio ottico la layout ODT. L&#39;angolo di incrocio del ODT è 2θ = 12 °. Il laser a fibra AFG controlla la pulsazione del laser, l&#39;AFG ODT controlla la trappola abbassamento curva, e la modulazione parametrica AFG controlla la modulazione dell&#39;intensità del laser. La vita di fascio di entrambi i fasci è di circa 37 um. La polarizzazione del primo fascio è verticale e la polarizzazione della seconda trave orizzontale. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55409/55409fig8large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> <img alt="Figura 9" src="/files/ftp_upload/55409/55409fig9.jpg" /> Figura 9: Tempomisurazione dipendenza del raffreddamento parametrica. a) Le immagini di assorbimento delle nubi atomiche di vari momenti di modulazione. b) La dipendenza di E (x, z) / E F in tempo modulazione (cerchi blu sono per E z / E F ei quadrati rossi sono per E x / E F). La figura inserto è il numero di atomi in funzione del tempo di modulazione. Le barre di errore rappresentano una deviazione standard. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55409/55409fig9large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> <table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody><tr><td> MOT caricamento su </td><td> Punto di partenza </td></tr><tr><td> tempo di caricamento MOT </td><td> 10 s </td></tr><tr><td> MOT raffreddamento </td><td> MOT carico off </td></tr><tr><td> tempo di raffreddamento MOT </td><td> 5 ms </td></tr><tr><td> MOT pompaggio su </td><td> MOT raffreddamento off </td></tr><tr><td> tempo MOT di pompaggio </td><td> 100 ms </td></tr><tr><td> MOT AOM off </td><td> MOT off (lo stesso MOT pompaggio off) </td></tr><tr><td> otturatore fascio lento Zeeman sulla </td><td> 200 ms prima MOT carico off </td></tr><tr><td> fascio MOT otturatore sulla </td><td> MOT off </td></tr><tr><td> Fibra laser raffreddamento evaporativo ora di inizio </td><td> 14 ms prima della fine del MOT loading </td></tr><tr><td> ODT raffreddamento evaporativo ora di inizio </td><td> 500 ms dopo MOT off </td></tr><tr><td> H-bridge tempo interruttore </td><td> MOT off </td></tr><tr><td> campo spazzata ora di inizio magnetica (da 0 a 330 g) </td><td> MOT off </td></tr><tr><td> ora di inizio del campo magnetico sweep (da 330 a 527.3G) </td><td> 2.000 ms dopo MOT off </td></tr><tr><td> ora di inizio Parametric raffreddamento </td><td> 2.500 ms dopo MOT off </td&gt; </tr><tr><td> Imaging tempo di impulso di innesco </td><td> 3.200 ms dopo MOT off </td></tr><tr><td> tempo di attivazione del CCD </td><td> 100 ms prima del tempo di attivazione dell&#39;impulso di imaging </td></tr></tbody></table> Tabella 1: controllo di temporizzazione sperimentale. Parametri di temporizzazione di sequenza per controllare strumenti sperimentali. La sequenza di temporizzazione inizia MOT carico, raffreddamento e pompaggio. Il fuori MOT è il punto di tempo di dopo MOT di pompaggio. <table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody><tr><td> Canale 1 </td><td> Canale 2 </td><td> Canale 3 </td><td> Channel 4 </td><td> Canale 5 </td></tr><tr><td> 348 ° C </td><td> 354 ° C </td><td> 434 ° C </td><td> 399 ° C </td><td> 372 ° C </td></tr></tbody></table> Tabella 2: Oveprofilo di temperatura n. Il forno 6 Li funziona a flusso ottimale con temperature elencate. <table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody><tr><td> Fase </td><td colspan="2"> Caricamento in corso </td><td colspan="2"> Raffreddamento </td><td colspan="2"> Pumping </td></tr><tr><td> Fascio </td><td> Raffreddamento </td><td> Repumping </td><td> Raffreddamento </td><td> Repumping </td><td> Raffreddamento </td><td> Repumping </td></tr><tr><td> Detuning dalla transizione bloccato (MHz) </td><td> -28 </td><td> -28 </td><td> -5 </td><td> -5 </td><td> -2 </td><td> OFF </td></tr><tr><td> Intensità (mi sono seduto) </td><td> 2 </td><td> 1 </td><td> 0.1 </td><td> 0.05 </td><td> 0,08 </td><td> OFF </td></tr></tbody></table> Tabella 3: fasi MOT proprietà. La sequenza delle fasi MOT è progettato per massimizzare the numero di atomi da trasferire nel ODT.

Watch this Scientific Journal Video about Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving at JoVE.com

Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving

We present a parametric driving method to cool an ultracold Fermi gas in a crossed-beam optical dipole trap. This method selectively removes high-energy atoms from the trap by periodically modulating the trap depth with frequencies that are resonant with the anharmonic components of the trapping potential.

Raffreddamento un otticamente Intrappolato ultrafreddi Fermi gas da guida periodica

We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs ...

cooling-an-optically-trapped-ultracold-fermi-gas-by-periodical-driving

Nanyang Technological University

Research

JoVE Journal

Engineering

7.4K Views.  Indiana University–Purdue University Indianapolis (IUPUI). We present a parametric driving method to cool an ultracold Fermi gas in a crossed-beam optical dipole trap. This method selectively removes high-energy atoms from the trap by periodically modulating the trap depth with frequencies that are resonant with the anharmonic components of the trapping potential. 

Video: Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving

Hyperpolarized Xenon for NMR and MRI Applications

Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 T generate only a small detectable net-magnetization of the sample at room temperature 1. Hence, most NMR and MRI applications rely on the detection of molecules at relative high concentration (e.g., water for imaging of biological tissue) or require excessive acquisition times. This limits our ability to exploit the very useful molecular specificity of NMR signals for many biochemical and medical applications. However, novel approaches have emerged in the past few years: Manipulation of the detected spin species prior to detection inside the NMR/MRI magnet can dramatically increase the magnetization and therefore allows detection of molecules at much lower concentration 2.
Here, we present a method for polarization of a xenon gas mixture (2-5% Xe, 10% N2, He balance) in a compact setup with a ca. 16000-fold signal enhancement. Modern line-narrowed diode lasers allow efficient polarization 7 and immediate use of gas mixture even if the noble gas is not separated from the other components. The SEOP apparatus is explained and determination of the achieved spin polarization is demonstrated for performance control of the method.
The hyperpolarized gas can be used for void space imaging, including gas flow imaging or diffusion studies at the interfaces with other materials 8,9. Moreover, the Xe NMR signal is extremely sensitive to its molecular environment 6. This enables the option to use it as an NMR/MRI contrast agent when dissolved in aqueous solution with functionalized molecular hosts that temporarily trap the gas 10,11. Direct detection and high-sensitivity indirect detection of such constructs is demonstrated in both spectroscopic and imaging mode.

The production of hyperpolarized xenon by means of spin exchange optical pumping (SEOP) is described. This method yields a ~10000-fold enhancement of the nuclear spin polarization of Xe-129 and has applications in nuclear magnetic resonance spectroscopy and imaging. Examples of gas phase and solution state experiments are given.

Xenon iperpolarizzato per NMR e applicazioni MRI

Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 ...

Ricerca

Ingegneria

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

Trapping ottica di nanoparticelle

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

Gradient Echo Quantum Memory in Warm Atomic Vapor

Gradient echo memory (GEM) is a protocol for storing optical quantum states of light in atomic ensembles. The primary motivation for such a technology is that quantum key distribution (QKD), which uses Heisenberg uncertainty to guarantee security of cryptographic keys, is limited in transmission distance. The development of a quantum repeater is a possible path to extend QKD range, but a repeater will need a quantum memory. In our experiments we use a gas of rubidium 87 vapor that is contained in a warm gas cell. This makes the scheme particularly simple. It is also a highly versatile scheme that enables in-memory refinement of the stored state, such as frequency shifting and bandwidth manipulation. The basis of the GEM protocol is to absorb the light into an ensemble of atoms that has been prepared in a magnetic field gradient. The reversal of this gradient leads to rephasing of the atomic polarization and thus recall of the stored optical state. We will outline how we prepare the atoms and this gradient and also describe some of the pitfalls that need to be avoided, in particular four-wave mixing, which can give rise to optical gain.

The gradient echo memory is a protocol for storing optical quantum states of light in atomic ensembles. Quantum memory is a key element of a quantum repeater, which can extend the range of quantum key distribution. We outline the operation of the scheme when implemented in a 3-level atomic ensemble.

Gradient Echo Quantum Memoria in Warm Atomic Vapor

Gradient  echo memory (GEM) is a protocol for storing optical quantum states of light in  atomic ensembles. The primary motivation for such a technology ...

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and&#160;limits the&#160;resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

Fabbricazione e funzionamento di un nano-ottica Nastro trasportatore

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization.

The fabrication process and experimental characterization techniques relevant to single-electron pumps based on silicon metal-oxide-semiconductor quantum dots are discussed.

Silicio metallico-ossido-semiconduttore Quantum Dots per singolo elettrone di pompaggio

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by ...

Direct Imaging of Laser-driven Ultrafast Molecular Rotation

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb explosion imaging setup in which a hitherto-impractical camera angle is realized. In our imaging technique, diatomic molecules are irradiated with a circularly polarized strong laser pulse. The ejected atomic ions are accelerated perpendicularly to the laser propagation. The ions lying in the laser polarization plane are selected through the use of a mechanical slit and imaged with a high-throughput, 2-dimensional detector installed parallel to the polarization plane. Because a circularly polarized (isotropic) Coulomb exploding pulse is used, the observed angular distribution of the ejected ions directly corresponds to the squared rotational wave function at the time of the pulse irradiation. To create a real-time movie of molecular rotation, the present imaging technique is combined with a femtosecond pump-probe optical setup in which the pump pulses create unidirectionally rotating molecular ensembles. Due to the high image throughput of our detection system, the pump-probe experimental condition can be easily optimized by monitoring a real-time snapshot. As a result, the quality of the observed movie is sufficiently high for visualizing the detailed wave nature of motion. We also note that the present technique can be implemented in existing standard ion imaging setups, offering a new camera angle or viewpoint for the molecular systems without the need for extensive modification.

We present a protocol for creating a real-time movie of a molecular rotational wave packet using a high-resolution Coulomb explosion imaging setup.

Direct Imaging di laser-driven ultraveloce rotazione molecolare

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb ...

Chimica

Optical Trap Loading of Dielectric Microparticles In Air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

Optical Trappola Caricamento di dielettrico microparticelle in aria

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 &#181;m-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

This paper presents a microfabrication methodology for surface ion traps, as well as a detailed experimental procedure for trapping ytterbium ions in a room-temperature environment.

Metodi sperimentali per intrappolare gli ioni utilizzando microfabbricati trappole ioniche in superficie

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due ...

Construction and Operation of a Light-driven Gold Nanorod Rotary Motor System

The possibility to generate and measure rotation and torque at the nanoscale is of fundamental interest to the study and application of biological and artificial nanomotors and may provide new routes towards single cell analysis, studies of non-equilibrium thermodynamics, and mechanical actuation of nanoscale systems. A facile way to drive rotation is to use focused circularly polarized laser light in optical tweezers. Using this approach, metallic nanoparticles can be operated as highly efficient scattering-driven rotary motors spinning at unprecedented rotation frequencies in water.
In this protocol, we outline the construction and operation of circularly-polarized optical tweezers for nanoparticle rotation and describe the instrumentation needed for recording the Brownian dynamics and Rayleigh scattering of the trapped particle. The rotational motion and the scattering spectra provides independent information on the properties of the nanoparticle and its immediate environment. The experimental platform has proven useful as a nanoscopic gauge of viscosity and local temperature, for tracking morphological changes of nanorods and molecular coatings, and as a transducer and probe of photothermal and thermodynamic processes.

Plasmonic gold nanorods can be trapped in liquids and rotated at kHz frequencies using circularly-polarized optical tweezers. Introducing tools for Brownian dynamics analysis and light scatteringspectroscopy leads to a powerful system for research and application in numerous fields of science.

Costruzione e funzionamento di un sistema motore basato su luce oro Nanorod Rotary

The possibility to generate and measure rotation and torque at the nanoscale is of fundamental interest to the study and application of biological and ...

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Accurate control of the polarization states of laser light is important in precision measurement experiments. In experiments involving the use of a vacuum environment, the stress-induced birefringence effect of the vacuum windows will affect the polarization states of laser light inside the vacuum system, and it is very difficult to measure and optimize the polarization states of the laser light in situ. The purpose of this protocol is to demonstrate how to optimize the polarization states of the laser light based on the fluorescence of ions in the vacuum system, and how to calculate the birefringence of vacuum windows based on azimuthal angles of external wave plates with Mueller matrix. The fluorescence of 25Mg+ ions induced by laser light that is resonant with the transition of |32P3/2,F = 4, mF&#160;= 4<img align="center" alt="Equation 100" src="/files/ftp_upload/61175/61175img1.jpg" style="color: rgb(68, 0, 68); font-size: 18px; font-weight: 700;" />&#160;&#8594;&#160;|32S1/2,F = 3, mF&#160;= 3<img align="center" alt="Equation 100" src="/files/ftp_upload/61175/61175img1.jpg" style="color: rgb(68, 0, 68); font-size: 18px; font-weight: 700;" />&#160;is sensitive to the polarization state of the laser light, and maximum fluorescence will be observed with pure circularly polarized light. A combination of half-wave plate (HWP) and quarter-wave plate (QWP) can achieve arbitrary phase retardation and is used for compensating the birefringence of the vacuum window. In this experiment, the polarization state of the laser light is optimized based on the fluorescence of 25Mg+ ion with a pair of HWP and QWP outside the vacuum chamber. By adjusting the azimuthal angles of the HWP and QWP to obtain maximum ion fluorescence, one can obtain a pure circularly polarized light inside the vacuum chamber. With the information on the azimuthal angles of the external HWP and QWP, the birefringence of the vacuum window can be determined.

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Presented here is a method to measure the birefringence of vacuum windows by maximizing the fluorescence counts emitted by Doppler cooled 25Mg+ ions in an ion trap. The birefringence of vacuum windows will change the polarization states of the laser, which can be compensated by changing the azimuthal angles of external wave plates.

In Situ Misurazione della Finestra a vuoto Birefringence utilizzando 25Mg- Fluorescenza

Accurate control of the polarization states of laser light is important in precision measurement experiments. In experiments involving the use of a vacuum ...