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0answers
38 views

Can a naked eye see a single atom when it is resonantly driven by some laser beam? [duplicate]

Presumably, when the laser is strong enough, the fluorescence will be very strong too. So, is it possible to see a single atom with a naked eye?
4
votes
1answer
82 views

How does Sisyphus cooling work in a photon picture?

Some years ago, during my masters degree, I took a short course on cold matter, which included a component on laser cooling and trapping taught by Ed Hinds. On the lecture on Sisyphus cooling, he ...
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0answers
18 views

Is absorption imaging in ultracold gases (BEC) a method destructive of the system?

As of title, I wonder whether this imaging method heats the gas up to the loss of quantum coherence. Let's consider a specific example, a gas of 87Rb (Rubidium) and its D2 line. I might be wrong in ...
0
votes
1answer
51 views

Thomas-Fermi approximation for cold atoms in a 1D harmonic potential

The Time-independent Gross-Pitaevskii equation is $$ \mu{\phi(x)}=\Big(\frac{-\hbar^{2}}{2m}\nabla^{2}+V_{ext}(x)+g|\phi(x)|^{2}\Big)\phi(x) $$ From Thomas-Fermi approximation, $$ ...
4
votes
0answers
40 views

Natural linewidth of hyperfine levels?

The D2 line of $^{87}Rb$ is the transition between the $5^2$$P_{3/2}$ and the $5^2$$S_{1/2}$ states. Its linewidth $\Gamma$ is always quoted to be $\sim 6 MHz$. But both states have hyperfine ...
3
votes
2answers
33 views

Frequency modulation in laser locking - what frequency?

In laser locking, e.g. using the PDH technique, the light (say of frequency $f$) is modulated so as to add two symmetric sidebands of frequency $\Omega$. I know the maths, I understand how this leads ...
0
votes
1answer
14 views

Why the total nuclear spin is only 0 or 2 for singlet s-wave scatting with $M_F=0$?

when I read the lecture of Feshbach resonance, the lecture on page 15 said that it want to find all s-wave molecules for $M_F=0$. It said when the two atoms are singlet, the total nuclear spin is only ...
5
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0answers
77 views

How to perform stroboscopic measurements for Floquet topological insulators?

Floquet topological insulators (arXiv:1008.1792, arXiv:1211.5623) have attracted much research interests in condensed matter physics. The goal is to realize topological insulators from trivial ...
1
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0answers
25 views

Can we 'dope' a fluid to make it become a superfluid?

The only element that can become a superfluid is Helium (He-3 and He-4) since it does not solidify not matter how cold it gets, hence it can reach the superfluid transition temperature whilst still a ...
0
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0answers
57 views

$U(1)$ gauge symmetry in superfluid

The conventional superfluid phase in a Bose-Hubbard ground state has $U(1)$ symmetry. In the presence of spin-orbit coupling (SOC), the superfluid ground state has non-uniform phases. Why do people in ...
1
vote
0answers
32 views

How is it possible to combine various techniques in cold atom experiments?

I’ve been reading about laser-trapped cold atoms (6Li in particular, which is a fermion) and was amazed at the number of things to keep track of in the experiments, just to gain that degree of control ...
3
votes
1answer
102 views

Interactions and scattering length in Feshbach resonances

In the context of cold atoms, one can make use of the Feshbach resonance mechanism to alter the sign and value of the two-particle scattering length by applying and varying an external magnetic field. ...
2
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0answers
62 views

Ground state symmetry breaking in Bose-Hubbard model with spin-orbit coupling

The Hamiltonian for 2D Bose-Hubbard model with spin-orbit coupling on a square lattice is written as $ H = -t\sum_{\langle ij \rangle}\Psi_i^{\dagger}\Psi_j^{\vphantom{\dagger}} + ...
3
votes
1answer
73 views

Can one make a synthetic dimension “curl around” into a cylinder?

A really cool recent proposal, Synthetic Gauge Fields in Synthetic Dimensions. A. Celi et al. Phys. Rev. Lett. 112, 043001 (2014), arXiv:1307.8349, shows how you can simulate a synthetic ...
3
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1answer
40 views

Why is the atom loss rate enhanced at the Feshbach resonance?

At the Feshbach resonance, the scattering length is enhanced. But why is the atom loss also enhanced?
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0answers
60 views

coherent states phase-space topology

Quantum mechanics can be formulated in various different ways. One of these is the so called phase space formulation, where we use quasi-probability distribution functions. The most recognized is the ...
0
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1answer
305 views

Proof of Kohn's theorem

In 1961 W. Kohn's paper ( Phys. Rev. 123, 1242 (1961) ) first stated that the electron-electron interaction does not change the cyclotron resonance frequency in a bulk three dimensional gas. I can ...
3
votes
1answer
79 views

When would the Gross-Pitaevskii equation break down as $a\rightarrow \infty$?

It is now common to use Feshbach resonance to tune the s-wave scattering length of a Bose-Einstein condensate. Apparently as $a\rightarrow \infty$, the GPE would break down. The reason is that it ...
0
votes
1answer
60 views

compressibility of cold atoms in optical lattices

The compressibility of cold bosons in an optical lattice is defined as $\kappa = \frac{\partial \langle n\rangle}{\partial \mu}$, where $\langle n\rangle$ is the density and $\mu$ is the chemical ...
2
votes
1answer
291 views

Superfluid-Mott insulator transition in Bose-Hubbard model in terms of vortex condensation

I have heard that there is some effective field theoretic type understanding of the superfluid-Mott insulator transition in Bose-Hubbard model. It says if the system is in a superfluid phase where the ...
1
vote
0answers
17 views

Effective Potential of experienced by a particle with contact interaction in an optical lattice

Suppose i have an optical lattice with particles loaded onto it, the potential due to the optical lattice is $V_{0}Cos\left(x\right)$. Assume that the particles interact with eachother through contact ...
4
votes
0answers
55 views

How to distinguish Bose glass and superfluid phases in a harmonic trap?

In mean-field study of Bose-Hubbard model in an optical lattice, what parameter can be calculated to distinguish Bose glass and superfluid in a harmonic trap?
0
votes
1answer
99 views

Thomas-Fermin approximation of cold atoms in a harmonic trap

In Bose-Hubbard model of cold atoms, one can use Thomas-Fermi approximation to get a rough number of total particle number. In Thomas-Fermi approximation, the site density is $n(R_i)=(\mu-\kappa ...
1
vote
1answer
41 views

Why the trap is needed in cold atom experiment?

In ultracold atomic gas experiments, the optical lattice provides a periodic optical potential to trap the atoms, why an extra trap, usually a harmonic trap is needed to trap the atoms?
2
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0answers
45 views

How to load Bose-Einstein Condensates into an optical lattice?

In cold atom experiments, what techniques are used to load Bose-Einstein Condensates into an optical lattice??
0
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0answers
240 views

Gutzwiller mean-field method in Bose Hubbard model

Gutzwiller mean-felid method is an efficient way to study Bose-Hubabrd model in optical lattice with a harmonic trap. Gutzwiller method assumes there is no spatial correlation within the trap, so ...
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0answers
36 views

Experimental Measurement of Quantum phase transition in an optical lattice

In Greiner and coauthors' seminal paper, the cold atoms are confined in a harmonic trap. So different many-body phases may coexist in the trap at a given lattice depth. For a deep lattice, there will ...
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votes
0answers
139 views

What is the difference between atomic limit and hard core boson limit?

In Bose-Hubbard model, we neglect the hopping term in atomic limit (U>>t) and the dominant interaction term result in a Mott Insulator phase. In hard core boson limit ($U \rightarrow \infty$), there ...
1
vote
1answer
146 views

Nomenclature clarification concerning solitons

My experience with solitons is restricted to the classical setting, namely solutions to the quartic interaction $\phi^4$, the Sine-Gordon equation, and Korteweg–de Vries equations. I was explicit to ...
19
votes
3answers
801 views

Are the recently observed Dirac monopoles separable?

I just went through Observation of Dirac monopoles in a synthetic magnetic field. What exactly has been observed? More importantly, are these monopoles localized inside the apparatus (no stray ...
1
vote
1answer
263 views

Coupling of open and closed channels in Feshbach resonance model

Feshbach resonance is described with coupling of 2 systems differing in the form of potentials :- one is said to produce a bound state (in 'closed' channel) and other is to produce scattering states ...
0
votes
2answers
118 views

What is a degenerate Fermi gas?

In ultracold atoms, it is generally talked of a degenerate Fermi gas. What does degenerate mean here?
-1
votes
2answers
856 views

Quantum Quench Problem

I read about the quantum quench problem in condensed matter physics. But what does really mean? Has anybody a good explanation about the origin of quantum quench problem?
4
votes
2answers
107 views

How to realize long-range interaction of colds atom in an optical lattice?

In the Bose-Hubbard model of cold atoms in an optical lattice, we consider only the short-range interaction or on-site interaction. Is it possible to realize long-range interaction similar to Coulomb ...
4
votes
1answer
216 views

Correct way to do a Thomas-Fermi approximation for cold gases

I have calculated the total Gross-Pitaevskii energy for a 2D Bose-Einstein condensate in an harmonical trap, using a variational gaussian wave function with a variational parameter b. Now I want to ...
1
vote
0answers
60 views

Single-site superfluid wave function and coherent state

The Superfluid wavefunction in Bose Hubbard model can be written as $|\Psi_{SF}\rangle=\frac{1}{\sqrt{N!}}(b_{k=0}^{\dagger})^N|0\rangle$ in the U=0 limit, whereU is the onsite interaction, N is the ...
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0answers
156 views

relative phase/sign in $\Psi$ after exchange of composite particles with angular momenta

I'm reading Quantum Liquids by A.J. Leggett and became confused by the following statement in the first chapter. Consider now a pair of such identical atoms. In the absence of appreciable coupling ...
1
vote
2answers
185 views

How does one subtract two light beams?

From what I understand, it seems like you can only "add" beams together. You can use a beam combiner, basically using a beam splitter in reverse, to combine two beams. In homodyne detection, you use a ...
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vote
0answers
103 views

2-body interaction energy of 3 particles

If only two-body interaction is considered then what's the energy if I put three particles on one site? Assume delta-interaction and interaction strength is proportional to scattering length $a_F$ ...
1
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0answers
51 views

Why is low temperature required for optical lattice systems to enter magnetic regime?

"Optical lattice requires a very low temperature scale to enter magnetism regime." Why is that? What I know: optical lattice systems suppress kinetic energy (hopping parameter: $t$ small); ...