71 research outputs found
Correlation-induced phase transitions and mobility edges in an interacting non-Hermitian quasicrystal
Non-Hermitian quasicrystal constitutes a unique class of disordered open
system with PT-symmetry breaking, localization and topological triple phase
transitions. In this work, we uncover the effect of quantum correlation on
phase transitions and entanglement dynamics in non-Hermitian quasicrystals.
Focusing on two interacting bosons in a Bose-Hubbard lattice with
quasiperiodically modulated gain and loss, we find that the onsite interaction
between bosons could drag the PT and localization transition thresholds towards
weaker disorder regions compared with the noninteracting case. Moreover, the
interaction facilitates the expansion of the critical point of a triple phase
transition in the noninteracting system into a critical phase with mobility
edges, whose domain could be flexibly controlled by tuning the interaction
strength. Systematic analyses of the spectrum, inverse participation ratio,
topological winding number, wavepacket dynamics and entanglement entropy lead
to consistent predictions about the correlation-driven phases and transitions
in our system. Our findings pave the way for further studies of the interplay
between disorder and interaction in non-Hermitian quantum matter.Comment: 18 pages, 13 figures, revised versio
A quantum circuit simulator and its applications on Sunway TaihuLight supercomputer
Classical simulation of quantum computation is vital for verifying quantum
devices and assessing quantum algorithms. We present a new quantum circuit
simulator developed on the Sunway TaihuLight supercomputer. Compared with other
simulators, the present one is distinguished in two aspects. First, our
simulator is more versatile. The simulator consists of three mutually
independent parts to compute the full, partial and single amplitudes of a
quantum state with different methods. It has the function of emulating the
effect of noise and support more kinds of quantum operations. Second, our
simulator is of high efficiency. The simulator is designed in a two-level
parallel structure to be implemented efficiently on the distributed many-core
Sunway TaihuLight supercomputer. Random quantum circuits can be simulated with
40, 75 and 200 qubits on the full, partial and single amplitude, respectively.
As illustrative applications of the simulator, we present a quantum fast
Poisson solver and an algorithm for quantum arithmetic of evaluating
transcendental functions. Our simulator is expected to have broader
applications in developing quantum algorithms in various fields.Comment: 21 pages, 9 figure
Quantum-inspired Complex Convolutional Neural Networks
Quantum-inspired neural network is one of the interesting researches at the
junction of the two fields of quantum computing and deep learning. Several
models of quantum-inspired neurons with real parameters have been proposed,
which are mainly used for three-layer feedforward neural networks. In this
work, we improve the quantum-inspired neurons by exploiting the complex-valued
weights which have richer representational capacity and better non-linearity.
We then extend the method of implementing the quantum-inspired neurons to the
convolutional operations, and naturally draw the models of quantum-inspired
convolutional neural networks (QICNNs) capable of processing high-dimensional
data. Five specific structures of QICNNs are discussed which are different in
the way of implementing the convolutional and fully connected layers. The
performance of classification accuracy of the five QICNNs are tested on the
MNIST and CIFAR-10 datasets. The results show that the QICNNs can perform
better in classification accuracy on MNIST dataset than the classical CNN. More
learning tasks that our QICNN can outperform the classical counterparts will be
found.Comment: 12pages, 6 figure
Optimization and Noise Analysis of the Quantum Algorithm for Solving One-Dimensional Poisson Equation
Solving differential equations is one of the most promising applications of
quantum computing. Recently we proposed an efficient quantum algorithm for
solving one-dimensional Poisson equation avoiding the need to perform quantum
arithmetic or Hamiltonian simulation. In this letter, we further develop this
algorithm to make it closer to the real application on the noisy
intermediate-scale quantum (NISQ) devices. To this end, we first develop a new
way of performing the sine transformation, and based on it the algorithm is
optimized by reducing the depth of the circuit from n2 to n. Then, we analyze
the effect of common noise existing in the real quantum devices on our
algorithm using the IBM Qiskit toolkit. We find that the phase damping noise
has little effect on our algorithm, while the bit flip noise has the greatest
impact. In addition, threshold errors of the quantum gates are obtained to make
the fidelity of the circuit output being greater than 90%. The results of noise
analysis will provide a good guidance for the subsequent work of error
mitigation and error correction for our algorithm. The noise-analysis method
developed in this work can be used for other algorithms to be executed on the
NISQ devices.Comment: 20 pages, 9 figure
Enhanced Hanbury Brown and Twiss interferometry using parametric amplification
The Hanbury Brown and Twiss (HBT) interferometer was proposed to observe intensity correlations of starlight to measure a star’s angular diameter. As the intensity of light that reaches the detector from a star is very weak, one cannot usually get a workable signal-to-noise ratio. We propose an improved HBT interferometric scheme incorporating optical parametric amplifiers (OPA) into the system to amplify the correlation signal. Remarkably, for weak star light, the signal-to-noise ratio (SNR) in the new HBT interferometric scheme is much better than that of conventional HBT interferometer. Our work is valuable in measuring a star whose intensity at the detector is low and maybe also applicable in remote sensing and long-distance quantum imaging where the light passed through the object is weak after a long distance transmission
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