New quantum algorithm for studying NP-complete problems

Complete quantum control of the population transfer branching ratio between two degenerate target states

A five-level four-pulse phase-sensitive extended stimulated Raman adiabatic passage scheme is proposed to realize complete control of the population transfer branching ratio between two degenerate target states. The control is achieved via a three-node null eigenstate that can be correlated with an arbitrary superposition of the target states. Our results suggest that complete suppression of the yield of one of two degenerate product states, and therefore absolute selectivity in photochemistry, is achievable and predictable, even without studying the properties of the unwanted product state be…

利用量子神经网络驱动的迭代 Harrow-Hassidim-Lloyd 算法研究少体簇团共振

Studying few cluster resonances with quantum neural network driven iterative Harrow-Hassidim-Lloyd algorithm

结合量子神经网络与迭代HHL算法（QNN-IHHL）解决量子多体问题，利用复标度和本征向量延拓技术在量子计算中研究少体簇团共振，以超核共振态为例验证了完全量子工作流程。

Studying chirality imbalance with quantum algorithms

To describe the chiral magnetic effect, the chiral chemical potential $μ_5$ is introduced to imitate the impact of topological charge changing transitions in the quark-gluon plasma under the influence of an external magnetic field. We employ the (1+1) dimensional Nambu-Jona-Lasinio (NJL) model to study the chiral phase structure and chirality charge density of strongly interacting matter with finite chiral chemical potential $μ_5$ in a quantum simulator. By performing the Quantum imaginary time evolution (QITE) algorithm, we simulate the (1+1) dimensional NJL model on the lattice at various te…

Similarity between Grover's quantum search algorithm and classical two-body collisions

By studying the attribute of the inversion about average operation in quantum searching algorithm, we find the similarity between the quantum searching and the course of two rigid bodies'collision. Some related questions are discussed from this similarity.

Demonstration of Minisuperspace Quantum Cosmology Using Quantum Computational Algorithms on IBM Quantum Computer

Quantum computers promise to efficiently solve important problems that are intractable on a conventional computer. Quantum computational algorithms have the potential to be an exciting new way of studying quantum cosmology. In quantum cosmology, we learn about the dynamics of the universe without constructing a complete theory of quantum gravity. Since the universal wavefunction exists in an infinite-dimensional superspace over all possible 3D metrics and modes of matter configurations, we take minisuperspaces for our work by constraining the degrees of freedom to particular 3D metrics and uni…

Quantum Algorithms for Lowest Weight Paths and Spanning Trees in Complete Graphs

Quantum algorithms for several problems in graph theory are considered. Classical algorithms for finding the lowest weight path between two points in a graph and for finding a minimal weight spanning tree involve searching over some space. Modification of classical algorithms due to Dijkstra and Prim allows quantum search to replace classical search and leads to more efficient algorithms. In the case of highly asymmetric complete bipartite graphs, simply replacing classical search with quantum search leads to a faster quantum algorithm. A fast quantum algorithm for computing the diameter of a …

时间序：用于研究闭合类时曲线量子模型的Python包

Qhronology: A Python package for studying quantum models of closed timelike curves

Qhronology是一个用于研究闭合类时曲线量子模型的Python科学计算包，提供分析量子抗时间旅行理论的框架，包含计算量子时间悖论解决方案的功能，并作为量子电路模拟器用于研究量子算法和协议。

Studying quantum algorithms for particle track reconstruction in the LUXE experiment

The LUXE experiment (LASER Und XFEL Experiment) is a new experiment in planning at DESY Hamburg, which will study Quantum Electrodynamics (QED) at the strong-field frontier. In this regime, QED is non-perturbative. This manifests itself in the creation of physical electron-positron pairs from the QED vacuum. LUXE intends to measure the positron production rate in this unprecedented regime by using, among others, a silicon tracking detector. The large number of expected positrons traversing the sensitive detector layers results in an extremely challenging combinatorial problem, which can become…

选择性Wigner相空间层析及其在量子混沌研究中的应用

Selective Wigner phase space tomography and its application for studying quantum chaos

本文提出选择性Wigner相空间层析（SWPST），利用Wigner矩阵的稀疏性高效重构量子态，并通过NMR实验在量子混沌kicked top模型中提取量子-经典对应特征。

Quantum Graph Homomorphisms via Operator Systems

We explore the concept of a graph homomorphism through the lens of C$^*$-algebras and operator systems. We start by studying the various notions of a quantum graph homomorphism and examine how they are related to each other. We then define and study a C$^*$-algebra that encodes all the information about these homomorphisms and establish a connection between computational complexity and the representation of these algebras. We use this C$^*$-algebra to define a new quantum chromatic number and establish some basic properties of this number. We then suggest a way of studying these quantum graph …

NP-complete Problems and Physical Reality

Can NP-complete problems be solved efficiently in the physical universe? I survey proposals including soap bubbles, protein folding, quantum computing, quantum advice, quantum adiabatic algorithms, quantum-mechanical nonlinearities, hidden variables, relativistic time dilation, analog computing, Malament-Hogarth spacetimes, quantum gravity, closed timelike curves, and "anthropic computing." The section on soap bubbles even includes some "experimental" results. While I do not believe that any of the proposals will let us solve NP-complete problems efficiently, I argue that by studying them, we …

Studying dynamics in two-dimensional quantum lattices using tree tensor network states

We analyze and discuss convergence properties of a numerically exact algorithm tailored to study the dynamics of interacting two-dimensional lattice systems. The method is based on the application of the time-dependent variational principle in a manifold of binary and quaternary Tree Tensor Network States. The approach is found to be competitive with existing matrix product state approaches. We discuss issues related to the convergence of the method, which could be relevant to a broader set of numerical techniques used for the study of two-dimensional systems.

Tensor-entanglement renormalization group approach to 2D quantum systems

Traditional mean-field theory is a simple generic approach for understanding various phases. But that approach only applies to symmetry breaking states with short-range entanglement. In this paper, we describe a generic approach for studying 2D quantum phases with long-range entanglement (such as topological phases). Our approach is a variational method that uses tensor product states (also known as projected entangled pair states) as trial wave functions. We use a 2D real space RG algorithm to evaluate expectation values in these wave functions. We demonstrate our algorithm by studying severa…