Classical images as quantum entanglement: An image processing analogy of the GHZ experiment

In this paper we present an optical analogy of quantum entanglement by means of classical images. As in previous works, the quantum state of two or more qbits is encoded by using the spatial modulation in amplitude and phase of an electromagnetic field. We show here that bidimensional encoding of two qbit states allows us to interpret some non local features of the joint measurement by the assumption of “astigmatic” observers with different resolving power in two orthogonal directions. As an application, we discuss the optical simulation of measuring a system characterized by multiparticle entanglement. The simulation is based on a local representation of entanglement and a classical interferometric system. In particular we show how to simulate the Greenberger-Horne Zeilinger (GHZ) argument and the experimental results which interpretation illustrates the conflict between quantum mechanics and local realism.     

Probing loop quantum gravity with evaporating black holes

This Letter aims at showing that the observation of evaporating black holes should allow the usual Hawking behavior to be distinguished from loop quantum gravity (LQG) expectations. We present a full Monte Carlo simulation of the evaporation in LQG and statistical tests that discriminate between competing models. We conclude that contrarily to what was commonly thought, the discreteness of the area in LQG leads to characteristic features that qualify evaporating black holes as objects that could reveal quantum gravity footprints.     

基于光晶格的超冷原子量子模拟

文章从超冷原子研究的视角出发,回顾了用“从下到上”的方案来开展量子模拟研究的历史.超冷原子作为宏观量子态,各个自由度精确可控,是量子模拟的绝佳平台.光晶格将冷原子物理和凝聚态物理融合起来,是其中最重要的技术之一,为超冷原子量子模拟提供了一个扎实的落脚点.近年来,关于拓扑量子模拟的研究日益兴起,成为超冷原子量子模拟新的重...     

Novel Quantum Video Steganography and Authentication Protocol with Large Payload

This paper proposed a secure authenticated quantum video steganography protocol with large capacity. The new protocol can embed secret quantum information into carrier quantum video, and expand the embedding capacity to a large extent. It also manages to accomplish quantum information steganography process based on unique features of video as well as authentication mechanism for better security. Finally, the simulation experiment proves that the new protocol not only has good performance on imperceptibility and security, but also owns a large capacity.     

Efficient quantum simulation of open quantum dynamics at various Hamiltonians and spectral densities

Simulation of open quantum dynamics for various Hamiltonians and spectral densities are ubiquitous for studying various quantum systems. On a quantum computer, only log₂N qubits are required for the simulation of an N-dimensional quantum system, hence simulation in a quantum computer can greatly reduce the computational complexity compared with classical methods. Recently, a quantum simulation approach was proposed for studying photosynthetic light harvesting [npj Quantum Inf. 4, 52 (2018)]. In this paper, we apply the approach to simulate the open quantum dynamics of various photosynthetic systems. We show that for Drude–Lorentz spectral density, the dimerized geometries with strong couplings within the donor and acceptor clusters respectively exhibit significantly improved efficiency. We also demonstrate that the overall energy transfer can be optimized when the energy gap between the donor and acceptor clusters matches the optimum of the spectral density. The effects of different types of baths, e.g., Ohmic, sub-Ohmic, and super-Ohmic spectral densities are also studied. The present investigations demonstrate that the proposed approach is universal for simulating the exact quantum dynamics of photosynthetic systems.     

Bose condensation of two-dimensional dipolar excitons: Simulation by the quantum Monte Carlo method

The Bose condensation of two-dimensional dipolar excitons in quantum wells is numerically studied by the diffusion Monte Carlo simulation method. The correlation, microscopic, thermodynamic, and spectral characteristics are calculated. It is shown that, in structures of coupled quantum wells, in which low-temperature features of exciton luminescence have presently been observed, dipolar excitons form a strongly correlated system.     

Effective potential approach to modeling of 25 nm MOSFET devices

We present a thermodynamic approach to introducing quantum corrections to the classical transport picture in semiconductor device simulation. The approach leads to a modified Boltzmann equation with an effective quantum potential that takes into account the Hartree and the barrier contributions. We study the influence of the quantum effects on the device output current.     

Selected topics of quantum computing for nuclear physics

Nuclear physics,whose underling theory is described by quantum gauge field coupled with matter,is fundamentally important and yet is formidably challenge for simulation with classical computers.Quantum computing provides a perhaps transformative approach for studying and understanding nuclear physics.With rapid scaling-up of quantum processors as well as advances on quantum algorithms,the digital quantum simulation approach for simulating quantum gauge fields and nuclear physics has gained lots of attention.In this review,we aim to summarize recent efforts on solving nuclear physics with quantum computers.We first discuss a formulation of nuclear physics in the language of quantum computing.In particular,we review how quantum gauge fields(both Abelian and non-Abelian)and their coupling to matter field can be mapped and studied on a quantum computer.We then introduce related quantum algorithms for solving static properties and real-time evolution for quantum systems,and show their applications for a broad range of problems in nuclear physics,including simulation of lattice gauge field,solving nucleon and nuclear structures,quantum advantage for simulating scattering in quantum field theory,non-equilibrium dynamics,and so on.Finally,a short outlook on future work is given.     

Simulation of chemical isomerization reaction dynamics on a NMR quantum simulator

Quantum simulation can beat current classical computers with minimally a few tens of qubits. Here we report an experimental demonstration that a small nuclear-magnetic-resonance quantum simulator is already able to simulate the dynamics of a prototype laser-driven isomerization reaction using engineered quantum control pulses. The experimental results agree well with classical simulations. We conclude that the quantum simulation of chemical reaction dynamics not computable on current classical computers is feasible in the near future.     

Quantum Image Filtering in the Spatial Domain

Quantum image processing has developed rapidly in recent years. In this paper, we propose a framework of quantum image filtering in the spatial domain. We proved that a high quantum parallel method to correlate the image and the filter mask can be achieved, even though the quantum correlation of two sequences is physically impossible. In order to avoid this impossible, we use quantum addition operation instead of quantum multiplication. We provide the quantum circuit that can realize the filtering task and present several simulation results on grayscale images. The main advantage of the quantum version lies in the efficient correlation between the quantum image and the filter mask.     

Exploiting quantum parallelism to simulate quantum random many-body systems

We present an algorithm that exploits quantum parallelism to simulate randomness in a quantum system. In our scheme, all possible realizations of the random parameters are encoded quantum mechanically in a superposition state of an auxiliary system. We show how our algorithm allows for the efficient simulation of dynamics of quantum random spin chains with known numerical methods. We propose an experimental realization based on atoms in optical lattices in which disorder could be simulated in parallel and in a controlled way through the interaction with another atomic species.     

Quantum backreaction through the Bohmian particle

A novel solution to the quantum backreaction problem in a mixed quantum-classical simulation is provided using the Bohmian interpretation of quantum mechanics. The Bohmian backreaction is unique, computationally simple, features reaction channel branching, and easily gives the full classical limit. The Bohmian quantum-classical method is illustrated by application to a model of O2 interacting with a Pt surface.     

Quantum spin dynamics as a model for quantum computer operation

We study effects of the physical realization of quantum computers on their logical operation. Through simulation of physical models of quantum computer hardware, we analyze the difficulties that are encountered in programming physical realizations of quantum computers. Examples of logically identical implementations of the controlled-NOT operation and Grover's database search algorithm are used to demonstrate that the results of a quantum computation are unstable with respect to the physical realization of the quantum computer. We discuss the origin of these instabilities and discuss possibilities to overcome this, for practical purposes, fundamental limitation of quantum computers. Received 5 November 2001 and Received in final form 8 February 2002     

Graphene-like physics in optical lattices

Graphene has attracted enormous attention over the past years in condensed matter physics. The most interesting feature of graphene is that its low-energy excitations are relativistic Dirac fermions. Such feature is the origin of many topological properties in graphene-like physics. On the other hand, ultracold quantum gas trapped in an optical lattice has become a unique setting for quantum simulation of condensed matter physics. Here, we mainly review our recent work on quantum simulation of graphene-like physics with ultracold atoms trapped in a honeycomb or square optical lattice, including the simulation of Dirac fermions and quantum Hall effect with and without Landau levels. We also present the related experimental advances.     

Propagation of quantum states of light through absorbing and amplifying media

We describe how quantum features of light fields become modified upon propagation through absorbing and amplifying media. Both absorption and amplification add noise to a beam of light. We examine the extent to which quantum features remain after this noise is added. We also examine the question of whether certain quantum states are more robust than others against degradation due to loss. Quantum states of this sort would constitute an important resource for use in quantum information processing. We quantify this thought by determining how the integration time required to achieve a specified signal-to-noise ratio increases in the presence of transmission losses. We find that under certain circumstances the required integration time increases more rapidly with transmission loss for measurement strategies based on coincidence detection of entangled photons than for strategies based on the properties of squeezed light.     

Quantum manipulation of trapped ions in two dimensional coulomb crystals

We show that a large number of ions forming a 2D Coulomb crystal provides an almost ideal system for scalable quantum computation and quantum simulation. In particular, the coupling of the internal states to the motion of the ions transverse to the crystal plane allows one to implement two-qubit quantum gates. We analyze in detail the decoherence induced by anharmonic couplings, and show that very high gate fidelities can be achieved with current experimental setups.     

Berry’s phase for a spin 1/2 particle in the presence of topological defects

The relativistic quantum dynamics of a spinorial quantum particle in the presence of a chiral conical background is investigated. We study the gravitational Berry geometric quantum phase acquired by a spin 1/2 particle in the chiral cosmic string spacetime. We obtain the result that this phase depends on the global features of this spacetime. We also consider the case that a string possesses an internal magnetic flux and obtain the geometric quantum phase in this case. The spacetime of multiple chiral cosmic strings is considered and the relativistic Berry quantum phase is also obtained.     

Controlling of entropic uncertainty in open quantum system via proper placement of quantum register

We investigate the dynamical behaviors of quantum-memory-assisted entropic uncertainty and its lower bound in the amplitude-damping channel. The influences of different placement positions of the quantum register on the dynamics of quantum coherence, quantum entanglement, and quantum discord are analyzed in detail. The numerical simulation results show that the quantum register should be placed in the channel of the non-Markovian effect. This option is beneficial to reduce the entropic uncertainty and its lower bound. We also find that this choice does not change the evolution of the quantum coherence and quantum entanglement, but changes the dynamical process of the quantum discord of the system.These results show that quantum coherence, quantum entanglement, and quantum discord are different quantum resources with unique characteristics and properties, and quantum discord can play a key role in reducing the uncertainty of quantum systems.     

A new approach to the Einstein-Podolsky-Rosen paradox

Some new aspects of the EPR paradox are considered. We first show that the authors' argument, leading to the conclusion that quantum theory is incomplete, is based on a tacit assumption that may be questioned. We then investigate the non-local features of the EPR setup and point out an interesting connection between the nonlocality involved in the quantum correlations of pairs of particles and that of a single particle in quantum theory.