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.

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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. 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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>

The authors have nothing to disclose. Specific product and company citations are for the purpose of clarification only and are not an endorsement by the authors.

Presentamos un protocolo experimental para la refrigeración paramétrico de un gas de Fermi no interactúe y en una trampa óptica de haz cruzado. Los pasos críticos de este protocolo incluyen: En primer lugar, necesita ser refrigerado cerca de la temperatura degenerado mediante la reducción de la profundidad de atrapar el gas Fermi atrapados ópticamente. En segundo lugar, una frecuencia de modulación se elige que es resonante con el componente anarmónico del potencial de captura. En tercer lugar, la intensidad de...

En las dos últimas décadas, varias técnicas de enfriamiento se han desarrollado para la generación de condensados de Bose-Einstein (BEC) y degenerar gases de Fermi (DFG) de los vapores atómicos calientes 1, 2, 3, 4, 5. BEC y DFG son nuevos fases de la materia que existen en temperaturas extremadamente bajas, por lo general una millonésima de un grado por encima del cero absoluto de temperatura, muy inferiores a los que normalmente se encuentran en la tierra o en el espacio. Para obtener tales bajas temperaturas, la mayoría de los métodos de refrigeración se basan en la reducción del potencial de captura para enfriar por evaporación los átomos. Sin embargo, el esquema de reducción también disminuye la tasa de colisiones de los átomos, lo que limita la eficacia de la refrigeración cuando el gas alcanza el régimen cuántico 6. En este artículo, se presenta un método de &quot;expulsar&quot; para enfriar por evaporación un gas ultrafrío Fermi en un ODT sinla reducción de la profundidad de trampa. Este método se basa en nuestro reciente estudio de refrigeración paramétrico 7, que muestra varias ventajas en comparación con los regímenes de descenso 7, 8, 9. La idea clave del esquema paramétrico es emplear el anarmonicidad de la ODT-haz cruzado, que hace que los átomos más calientes cerca del borde del potencial de captura sienten las frecuencias de captura más bajos que los átomos más frías en el centro. Este anarmonicidad permite que los átomos más caliente al ser expulsados ​​selectivamente de la trampa cuando la modulación del potencial de captura en las frecuencias de resonancia con los átomos de alta energía. El protocolo experimental de enfriamiento paramétrico requiere un gas pre-enfriado noninteracting Fermi cerca de la temperatura degenerada. Para implementar este protocolo, un modulador acústico-óptico (AOM) se utiliza para modular la intensidad de los haces de captura por controlling la modulación de frecuencia, profundidad y tiempo. Para verificar el efecto de enfriamiento, la nube atómica se sonda de formación de imágenes por absorción de tiempo de vuelo (TOF), donde un haz de láser resonante ilumina la nube atómica y la sombra de absorción es capturada por un dispositivo acoplado de carga (CCD) de la cámara. Las propiedades de las nubes, como el número de átomos, la energía y la temperatura, se determinan por la densidad de la columna. Para caracterizar el efecto de enfriamiento, se mide la dependencia de las energías de la nube en los distintos momentos de modulación.

<table><tbody><tr><td>500 mW 671 nm ECDL</td><td>Toptica</td><td>TA Pro</td><td>Quantity: 1</td></tr><tr><td>35 mW 671 nm ECDL</td><td>Toptica</td><td>DL-100</td><td>Quantity: 1</td></tr><tr><td>671 nm AOM</td><td>Isomet</td><td>1206C</td><td>Quantity: 3</td></tr><tr><td>671 nm AOM Driver</td><td>Isomet</td><td>630C-110</td><td>Quantity: 3</td></tr><tr><td>100 W 1,064 nm CW laser</td><td>IPG photonics</td><td>YLR-100-1064-LP</td><td>Quantity: 1</td></tr><tr><td>1,064 nm AOM</td><td>IntraAction</td><td>ATM-804DA6B&amp;nbsp;</td><td>Quantity: 1</td></tr><tr><td>1,064 nm AOM Driver</td><td>IntraAction</td><td>ME-805EH&amp;nbsp;</td><td>Quantity: 1</td></tr><tr><td>Arbitrary Function Generator</td><td>Agilent&amp;nbsp;</td><td>33120A</td><td>Quantity: 3</td></tr><tr><td>Digital I/O Board</td><td>United Electronic Industries</td><td>PD2-DIO-128</td><td>Quantity: 1</td></tr><tr><td>System Design Platform</td><td>National Instruments</td><td>LabVIEW</td><td>Quantity: 1</td></tr><tr><td>Analog Voltage Output Device</td><td>Measurement Computing</td><td>USB-3104</td><td>Quantity: 1</td></tr><tr><td>CCD Camera</td><td>Hamamatsu</td><td>Orca R2</td><td>Quantity: 1</td></tr><tr><td>Arbitrary Pulse Generator</td><td>Quantum Composer</td><td>9618+</td><td>Quantity: 1</td></tr><tr><td>Analog Voltage Output Device</td><td>Measurement Computing</td><td>USB-3104</td><td>Quantity: 1</td></tr><tr><td>20 A power supply</td><td></td><td></td><td>Quantity: 1</td></tr><tr><td>10 A power supply</td><td></td><td></td><td>Quantity: 1</td></tr><tr><td>120 A power supply</td><td></td><td></td><td>Quantity: 2</td></tr><tr><td>Cooling Fans</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>671 nm Mirrors</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>671 nm Half-wave Plate</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>671 nm Quarter-wave Plate</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>500 mW Beam Shutter</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>671 nm Lenses</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>Faraday Isolator</td><td></td><td></td><td>Quantity: 2, one for each ECDL</td></tr><tr><td>671 nm Polarizing Beam Splitter</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>Photodetector</td><td>Thorlabs</td><td>SM05PD1A</td><td>Quantity: 1</td></tr><tr><td>Multiplexer&amp;nbsp;</td><td>Analog Devices</td><td>ADG409</td><td>Quantity: 1</td></tr><tr><td>Multiplexer&amp;nbsp;</td><td>Analog Devices</td><td>ADG408</td><td>Quantity: 2</td></tr><tr><td>1,064 nm plano-concave lens</td><td></td><td></td><td>Quantity: 1 for beam reducer</td></tr><tr><td>1,064 nm plano-convex lens</td><td></td><td></td><td>Quantity: 1 for beam reducer</td></tr><tr><td>1,064 nm Mirrors</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>1,064 nm Half-wave Plates</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>1,064 nm Lenses</td><td></td><td></td><td>Quantity: depends on apparatus design</td></tr><tr><td>1,064 nm Thin Film Polarizer</td><td></td><td></td><td>Quantity: 1</td></tr><tr><td>100 W, 1,064 nm Beam Dump</td><td></td><td></td><td>Quantity: 1</td></tr><tr><td>100 W, 1,064 nm Power Meter</td><td></td><td></td><td>Quantity: 1</td></tr><tr><td>RF Function Generator</td><td>Rigol</td><td>DG4162</td><td>Quantity: 1</td></tr><tr><td>RF Power Amplifier</td><td>Mini-Circuits</td><td>ZHL-100W-GAN+</td><td>Quantity: 1</td></tr></tbody></table>

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 este protocolo, estudiamos la dependencia de la refrigeración paramétrico en el tiempo de modulación con la frecuencia de modulación optimizada y amplitud, ambos de los cuales han sido determinados en nuestra publicación anterior 7. En primer lugar, preparamos un gas de Fermi noninteracting de 6 átomos de Li en los dos estados hiperfinos más bajas con una temperatura de T / T F ≈ 1,2. Aquí, T F</sub...

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.

Enfriar un ópticamente Atrapado ultrafrías Fermi de gas por conducción periódica

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

Research

JoVE Journal

Engineering

7.4K vistas.  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.

Xenón hiperpolarizado para RMN y MRI Aplicaciones

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

Investigación

Ingeniería

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.

Trampas ópticas de las nanopartículas

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 Memoria Quantum en Warm Atómica 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.

Fabricación y operación de una banda transportadora nano-óptica

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.

De silicio metal-óxido-semiconductor Quantum Dots para Bombeo solo electrón

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 del impulsada por el láser ultrarrápido Molecular Rotación

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

Química

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.

Cargando óptica Trampa de micropartículas en dieléctrica del aire

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.

Métodos experimentales para atrapar iones usando recientemente trampas de iones de la 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.

Construcción y operación de un sistema del Motor rotatorio de Nanorod oro impulsado por la luz

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 Medición de la Birefringencia de la Ventana de Vacío usando 25Mg+ Fluorescencia

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