228 research outputs found
A Non-stochastic Optimization Algorithm for Neural-network Quantum States
Neural-network quantum states (NQS) employ artificial neural networks to
encode many-body wave functions in second quantization through variational
Monte Carlo (VMC). They have recently been applied to accurately describe
electronic wave functions of molecules and have shown the challenges in
efficiency comparing with traditional quantum chemistry methods. Here we
introduce a general non-stochastic optimization algorithm for NQS in chemical
systems, which deterministically generates a selected set of important
configurations simultaneously with energy evaluation of NQS. This method
bypasses the need for Markov-chain Monte Carlo within the VMC framework,
thereby accelerating the entire optimization process. Furthermore, this
newly-developed non-stochastic optimization algorithm for NQS offers comparable
or superior accuracy compared to its stochastic counterpart and ensures more
stable convergence. The application of this model to test molecules exhibiting
strong electron correlations provides further insight into the performance of
NQS in chemical systems and opens avenues for future enhancements.Comment: 30 pages, 7 figures, and 1 tabl
High-dimensional frequency conversion in hot atomic system
One of the major difficulties in realizing a high-dimensional frequency
converter for conventional optical vortex (COV) stems from the difference in
ring diameter of COV modes with different topological charge numbers l. Here,
we implement a high-dimensional frequency convertor for perfect optical vortex
(POV) modes with invariant size through the four-wave mixing (FWM) process by
utilizing Bessel-Gaussian beams instead of Laguerre-Gaussian beams. The
measured conversion efficiency from 1530 nm to 795 nm is independent of l at
least in subspace of {-6,...,6}, and the achieved conversion fidelities for
two-dimensional (2D) superposed POV states exceed 97%. We further realize the
frequency conversion of 3D, 5D and 7D superposition states with fidelities as
high as 96.70%, 89.16% and 88.68%, respectively. The reported scheme is
implemented in hot atomic vapor, it's also compatible with the cold atomic
system and may find applications in high-capacity and long-distance quantum
communication
Optical Memory for Arbitrary Perfect Poincar\'e States in an Atomic Ensemble
Inherent spin angular momentum (SAM) and orbital angular momentum (OAM) which
manifest as polarization and spatial degrees of freedom (DOF) of photons, hold
a promise of large capability for applications in classical and quantum
information processing. To enable these photonic spin and orbital dynamic
properties strongly coupled with each other, Poincar\'{e} states have been
proposed and offer advantages in data multiplexing, information encryption,
precision metrology, and quantum memory. However, since the transverse size of
Laguerre Gaussian beams strongly depends on their topological charge numbers
, it is difficult to store asymmetric Poincar\'{e} states due
to the significantly different light-matter interaction for distinct spatial
modes. Here, we experimentally realize the storage of perfect Poincar\'{e}
states with arbitrary OAM quanta using the perfect optical vortex, in which 121
arbitrarily-selected perfect Poincar\'{e} states have been stored with high
fidelity. The reported work has great prospects in optical communication and
quantum networks for dramatically increased encoding flexibility of
information
Detection of infrared light through stimulated four-wave mixing process
Infrared optical measurement has a wide range of applications in industry and
science, but infrared light detectors suffer from high costs and inferior
performance than visible light detectors. Four-wave mixing (FWM) process allows
detection in the infrared range by detecting correlated visible light. We
experimentally investigate the stimulated FWM process in a hot Rb atomic
vapor cell, in which a weak infrared signal laser at nm induces the FWM
process and is amplified and converted into a strong FWM light at nm, the
latter can be detected more easily. We find the optimized single- and
two-photon detunings by studying the dependence of the frequency of input laser
on the generated FWM light. What's more, the power gain increases rapidly as
the signal intensity decreases, which is consistent with our theoretical
analysis. As a result, the power gain can reach up to 500 at a signal laser
power of W and the number of detected photons increased by a factor of
250. Finally, we experimentally prove that our amplification process can work
in a broad band in the frequency domain by exploring the response rate of our
stimulated FWM process.Comment: 4 figure
Experimental realization of quantum non-reciprocity based on cold atomic ensembles
In analog to counterparts widely used in electronic circuits, all optical
non-reciprocal devices are basic building blocks for both classical and quantum
optical information processing. Approaching the fundamental limit of such
devices, where the propagation of a single photon exhibits a good
non-reciprocal characteristic, requires an asymmetric strong coupling between a
single photon and a matter. Unfortunately it has been not realized yet. Here,
we propose and experimentally realize a quantum non-reciprocity device with low
optical losses and a high isolation of larger than 14 dB based on the cold
atoms. Besides, the non-reciprocal transmission of a quantum qubit and
non-reciprocal quantum storage of a true single photon are also realized. All
results achieved would be very promising in building up quantum non-reciprocal
devices for quantum networks.Comment: 7 pages, 4 figure
- …