473 research outputs found
Fast mode of rotating atoms in one-dimensional lattice rings
We study the rotation of atoms in one-dimensional lattice rings. In
particular, the "fast mode", where the ground state atoms rotate faster than
the stirring rotating the atoms, is studied both analytically and numerically.
The conditions for the transition to the fast mode are found to be very
different from that in continuum rings. We argue that these transition
frequencies remain unchanged for bosonic condensates described in a mean field.
We show that Fermionic interaction and filling factor have a significant effect
on the transition to the fast mode, and Pauli principle may suppress it
altogether.Comment: 4 pages, 5 figure
Optimal Stochastic Enhancement of Photoionization
The effect of noise on the nonlinear photoionization of an atom due to a
femtosecond pulse is investigated in the framework of the stochastic
Schr\"odinger equation. A modest amount of white noise results in an
enhancement of the net ionization yield by several orders of magnitude, giving
rise to a form of quantum stochastic resonance. We demonstrate that this effect
is preserved if the white noise is replaced by broadband chaotic light.Comment: 4 pages, 4 figure
Femtosecond Photoionization of Atoms under Noise
We investigate the effect of incoherent perturbations on atomic
photoionization due to a femtosecond mid-infrared laser pulse by solving the
time-dependent stochastic Schr\"odinger equation. For a weak laser pulse which
causes almost no ionization, an addition of a Gaussian white noise to the pulse
leads to a significantly enhanced ionization probability. Tuning the noise
level, a stochastic resonance-like curve is observed showing the existence of
an optimum noise for a given laser pulse. Besides studying the sensitivity of
the obtained enhancement curve on the pulse parameters, such as the pulse
duration and peak amplitude, we suggest that experimentally realizable
broadband chaotic light can also be used instead of the white noise to observe
similar features. The underlying enhancement mechanism is analyzed in the
frequency-domain by computing a frequency-resolved atomic gain profile, as well
as in the time-domain by controlling the relative delay between the action of
the laser pulse and noise.Comment: 10 pages, 10 figure
Nonlinear optics via double dark resonances
Double dark resonances originate from a coherent perturbation of a system
displaying electromagnetically induced transparency. We experimentally show and
theoretically confirm that this leads to the possibility of extremely sharp
resonances prevailing even in the presence of considerable Doppler broadening.
A gas of 87Rb atoms is subjected to a strong drive laser and a weak probe laser
and a radio frequency field, where the magnetic coupling between the Zeeman
levels leads to nonlinear generation of a comb of sidebands.Comment: 6 pages, 9 figure
Zero and Finite Temperature Quantum Simulations Powered by Quantum Magic
We present a comprehensive approach to quantum simulations at both zero and
finite temperatures, employing a quantum information theoretic perspective and
utilizing the Clifford + Rz transformations. We introduce the "quantum magic
ladder", a natural hierarchy formed by systematically augmenting Clifford
transformations with the addition of Rz gates. These classically simulable
similarity transformations allow us to reduce the quantumness of our system,
conserving vital quantum resources. This reduction in quantumness is essential,
as it simplifies the Hamiltonian and shortens physical circuit-depth,
overcoming constraints imposed by limited error correction. We improve the
performance of both digital and analog quantum computers on ground state and
finite temperature molecular simulations, not only outperforming the
Hartree-Fock solution, but also achieving consistent improvements as we ascend
the quantum magic ladder. By facilitating more efficient quantum simulations,
our approach enables near-term and early fault-tolerant quantum computers to
address novel challenges in quantum chemistry.Comment: 12 pages, 9 figure
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Pervasive selection for and against antibiotic resistance in inhomogeneous multistress environments
Antibiotic-sensitive and -resistant bacteria coexist in natural environments with low, if detectable, antibiotic concentrations. Except possibly around localized antibiotic sources, where resistance can provide a strong advantage, bacterial fitness is dominated by stresses unaffected by resistance to the antibiotic. How do such mixed and heterogeneous conditions influence the selective advantage or disadvantage of antibiotic resistance? Here we find that sub-inhibitory levels of tetracyclines potentiate selection for or against tetracycline resistance around localized sources of almost any toxin or stress. Furthermore, certain stresses generate alternating rings of selection for and against resistance around a localized source of the antibiotic. In these conditions, localized antibiotic sources, even at high strengths, can actually produce a net selection against resistance to the antibiotic. Our results show that interactions between the effects of an antibiotic and other stresses in inhomogeneous environments can generate pervasive, complex patterns of selection both for and against antibiotic resistance
Enhancing Detection of Topological Order by Local Error Correction
The exploration of topologically-ordered states of matter is a long-standing
goal at the interface of several subfields of the physical sciences. Such
states feature intriguing physical properties such as long-range entanglement,
emergent gauge fields and non-local correlations, and can aid in realization of
scalable fault-tolerant quantum computation. However, these same features also
make creation, detection, and characterization of topologically-ordered states
particularly challenging. Motivated by recent experimental demonstrations, we
introduce a new paradigm for quantifying topological states -- locally
error-corrected decoration (LED) -- by combining methods of error correction
with ideas of renormalization-group flow. Our approach allows for efficient and
robust identification of topological order, and is applicable in the presence
of incoherent noise sources, making it particularly suitable for realistic
experiments. We demonstrate the power of LED using numerical simulations of the
toric code under a variety of perturbations. We subsequently apply it to an
experimental realization, providing new insights into a quantum spin liquid
created on a Rydberg-atom simulator. Finally, we extend LED to generic
topological phases, including those with non-abelian order.Comment: Corrected minor typos. Added new results on generalizations to
non-abelian topological phases, and connections between LED and topological
entanglement negativit
Entanglement of Atomic Ensembles by Trapping Correlated Photon States
We describe a general technique that allows for an ideal transfer of quantum
correlations between light fields and metastable states of matter. The
technique is based on trapping quantum states of photons in coherently driven
atomic media, in which the group velocity is adiabatically reduced to zero. We
discuss possible applications such as quantum state memories, generation of
squeezed atomic states, preparation of entangled atomic ensembles and quantum
information processing
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