다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

This paper reviews recent experimental and theoretical progress concerning many-body phenomena in dilute, ultracold gases. It focuses on effects beyond standard weak-coupling descriptions, such as the Mott-Hubbard transition in optical lattices, strongly interacting gases in one and two dimensions, or lowest-Landau-level physics in quasi-two-dimensional gases in fast rotation. Strong correlations in fermionic gases are discussed in optical lattices or near-Feshbach resonances in the BCS-BEC crossover.

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Many-Body Physics with Ultracold Gases

Quantum networks provide opportunities and challenges across a range of intellectual and technical frontiers, including quantum computation, communication and metrology. The realization of quantum networks composed of many nodes and channels requires new scientific capabilities for generating and characterizing quantum coherence and entanglement. Fundamental to this endeavour are quantum interconnects, which convert quantum states from one physical system to those of another in a reversible manner. Such quantum connectivity in networks can be achieved by the optical interactions of single photons and atoms, allowing the distribution of entanglement across the network and the teleportation of quantum states between nodes.

The quantum internet

Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

We present a scheme of quantum computation that consists entirely of one-qubit measurements on a particular class of entangled states, the cluster states. The measurements are used to imprint a quantum logic circuit on the state, thereby destroying its entanglement at the same time. Cluster states are thus one-way quantum computers and the measurements form the program.

http://www2.fisica.unlp.edu.ar/materias/qc/RB2.pdf

A one-way quantum computer.

The electron is spherical — well, nearly. The standard model of particle physics predicts a slightly aspheric electron, with a distortion characterized by the electric dipole moment (EDM) that is far too small to be detected at current experimental sensitivities. However, some extensions to the standard model predict much larger EDM values that should be detectable. New experiments, using the dipolar ytterbium fluoride rather than spherical thallium, achieve the highest precision measurement of the EDM to date. At this new level of precision the EDM is consistent with zero, and the electron is indeed a sphere. This finding should help to constrain theories of particle physics and cosmology beyond the standard model. The electron is predicted to be slightly aspheric1, with a distortion characterized by the electric dipole moment (EDM), de. No experiment has ever detected this deviation. The standard model of particle physics predicts that de is far too small to detect2, being some eleven orders of magnitude smaller than the current experimental sensitivity. However, many extensions to the standard model naturally predict much larger values of de that should be detectable3. This makes the search for the electron EDM a powerful way to search for new physics and constrain the possible extensions. In particular, the popular idea that new supersymmetric particles may exist at masses of a few hundred GeV/c2 (where c is the speed of light) is difficult to reconcile with the absence of an electron EDM at the present limit of sensitivity2,4. The size of the EDM is also intimately related to the question of why the Universe has so little antimatter. If the reason is that some undiscovered particle interaction5 breaks the symmetry between matter and antimatter, this should result in a measurable EDM in most models of particle physics2. Here we use cold polar molecules to measure the electron EDM at the highest level of precision reported so far, providing a constraint on any possible new interactions. We obtain de = (−2.4 ± 5.7stat ± 1.5syst) × 10−28e cm, where e is the charge on the electron, which sets a new upper limit of |de| < 10.5 × 10−28e cm with 90 per cent confidence. This result, consistent with zero, indicates that the electron is spherical at this improved level of precision. Our measurement of atto-electronvolt energy shifts in a molecule probes new physics at the tera-electronvolt energy scale2.

https://slacportal.slac.stanford.edu/sites/ard_public/people/vibh/Documents/EDM/nature10104-2011-ImperialCollege.pdf

Improved measurement of the shape of the electron

The most sensitive measurements of the electron electric dipole moment ${d}_{e}$ have previously been made using heavy atoms. Heavy polar molecules offer a greater sensitivity to ${d}_{e}$ because the interaction energy to be measured is typically ${10}^{3}$ times larger than in a heavy atom. We have used YbF to make the first measurement of this kind. Together, the large interaction energy and the strong tensor polarizability of the molecule make our experiment essentially free of the systematic errors that currently limit ${d}_{e}$ measurements in atoms. Our first result ${d}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}0.2\ifmmode\pm\else\textpm\fi{}3.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}26}e\mathrm{cm}$ is less sensitive than the best atom measurement but is limited only by counting statistics and demonstrates the power of the method.

Measurement of the electron electric dipole moment using YbF molecules.

Magneto-optical trapping and sub-Doppler cooling of atoms has been instrumental for research in ultracold atomic physics. This regime has now been reached for a molecular species, CaF. Magneto-optical trapping and sub-Doppler cooling have been essential to most experiments with quantum degenerate gases, optical lattices, atomic fountains and many other applications. A broad set of new applications await ultracold molecules1, and the extension of laser cooling to molecules has begun2,3,4,5,6. A magneto-optical trap (MOT) has been demonstrated for a single molecular species, SrF7,8,9, but the sub-Doppler temperatures required for many applications have not yet been reached. Here we demonstrate a MOT of a second species, CaF, and we show how to cool these molecules to 50 μK, well below the Doppler limit, using a three-dimensional optical molasses. These ultracold molecules could be loaded into optical tweezers to trap arbitrary arrays10 for quantum simulation11, launched into a molecular fountain12,13 for testing fundamental physics14,15,16,17,18, and used to study collisions and chemistry19 between atoms and molecules at ultracold temperatures.

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Molecules cooled below the Doppler limit

We have studied the deflection of ground-state sodium atoms passing through a micron-sized parallel-plate cavity by measuring the intensity of a sodium atomic beam transmitted through the cavity as a function of cavity plate separation. This experiment provides clear evidence for the existence of the Casimir-Polder force, which is due to modification of the ground-state Lamb shift in the confined space of a cavity. Our results confirm the magnitude of the force and the distance dependence predicted by quantum electrodynamics.

/pdf/measurement-of-the-casimir-polder-force-3qhi9kzdiw.pdf

Measurement of the Casimir-Polder force.

We demonstrate slowing and longitudinal cooling of a supersonic beam of CaF molecules using counter-propagating laser light resonant with a closed rotational and almost closed vibrational transition. A group of molecules are decelerated by about 20 m/s by applying light of a fixed frequency for 1.8 ms. Their velocity spread is reduced, corresponding to a final temperature of about 300 mK. The velocity is further reduced by chirping the frequency of the light to keep it in resonance as the molecules slow down.

E. A. Hinds

Papers

Improved measurement of the shape of the electron

Measurement of the electron electric dipole moment using YbF molecules.

Molecules cooled below the Doppler limit

Measurement of the Casimir-Polder force.

Laser cooling and slowing of CaF molecules