Phase sensitive adiabatic states, or does the material phase recognize the physical reality?

量子宇宙中关于经典实在的共识

Consensus About Classical Reality in a Quantum Universe

该研究基于量子达尔文主义，利用信息论互信息度量量化观测者通过环境碎片获取系统信息时的共识，证明信息充足时观测者会就指针态达成一致，并通过模型与模拟验证，揭示经典世界从量子宇宙中涌现的机制。

Adiabatic eigenstate deformations as a sensitive probe for quantum chaos

In the past decades, it was recognized that quantum chaos, which is essential for the emergence of statistical mechanics and thermodynamics, manifests itself in the effective description of the eigenstates of chaotic Hamiltonians through random matrix ensembles and the eigenstate thermalization hypothesis. Standard measures of chaos in quantum many-body systems are level statistics and the spectral form factor. In this work, we show that the norm of the adiabatic gauge potential, the generator of adiabatic deformations between eigenstates, serves as a much more sensitive measure of quantum cha…

Is the Quantum State Real in the Hilbert Space Formulation?

The persistent debate about the reality of a quantum state has recently come under limelight because of its importance to quantum information and the quantum computing community. Almost all of the deliberations are taking place using the elegant and powerful but abstract Hilbert space formalism of quantum mechanics developed with seminal contributions from John von Neumann. Since it is rather difficult to get a direct perception of the events in an abstract vector space, it is hard to trace the progress of a phenomenon. Among the multitude of recent attempts to show the reality of the quantum …

Ab initio nuclear structure via quantum adiabatic algorithm

Background: Solving nuclear many-body problems with an ab initio approach is widely recognized as a computationally challenging problem. Quantum computers offer a promising path to address this challenge. There are urgent needs to develop quantum algorithms for this purpose. Objective: In this work, we explore the application of the quantum algorithm of adiabatic state preparation with quantum phase estimation in ab initio nuclear structure theory. We focus on solving the low-lying spectra (including both the ground and excited states) of simple nuclear systems. Ideas: The efficiency of this a…

自旋量子比特系统中非绝热量子控制在量子计算中的优势

Benefits of non-adiabatic quantum control in quantum computation through spin qubit systems

本文探讨了在自旋量子比特系统中实现非绝热控制对量子计算的固有优势，并指出混合量子-经典方法在未来五至十年内将主导市场，为量子计算进展开辟新窗口。

Protective Measurements

Protective measurements yield properties of the quantum state of a single quantum system without affecting the quantum state. A protective measurement involves adiabatic coupling to the measuring device together with a procedure to protect the state from changing. For nondegenerate energy eigenstates the protection is provided by the system itself. In this case it is actually possible to measure the Schrödinger wave via measurements on a single system. This fact provides an argument in favor of associating physical reality with a quantum state of a single system, challenging the usual ensemble…

Observable Dirac-type singularities in Berry's phase and the monopole

The physical reality and observability of 2nπBerry phases, as opposed to the usually considered modulo 2πtopological phases is demonstrated with the help of computer simulation of a model adiabatic evolution whose parameters are varied along a closed loop in the parameter space. Using the analogy of Berry's phase with the Dirac monopole, it is concluded that an interferometer loop taken around a magnetic monopole of strength n/2 yields an observable 2nπphase shift, where n is an integer. An experiment to observe the effect is proposed.

Einstein, incompleteness, and the epistemic view of quantum states

Does the quantum state represent reality or our knowledge of reality? In making this distinction precise, we are led to a novel classification of hidden variable models of quantum theory. Indeed, representatives of each class can be found among existing constructions for two-dimensional Hilbert spaces. Our approach also provides a fruitful new perspective on arguments for the nonlocality and incompleteness of quantum theory. Specifically, we show that for models wherein the quantum state has the status of something real, the failure of locality can be established through an argument considerab…

Graph isomorphism and adiabatic quantum computing

In the Graph Isomorphism problem two N-vertex graphs G and G' are given and the task is to determine whether there exists a permutation of the vertices of G that preserves adjacency and transforms G into G'. If yes, then G and G' are said to be isomorphic; otherwise they are non-isomorphic. The GI problem is an important problem in computer science and is thought to be of comparable difficulty to integer factorization. In this paper we present a quantum algorithm that solves arbitrary instances of GI and can also determine all automorphisms of a given graph. We show how the GI problem can be c…

Abelian and Non-Abelian Quantum Geometric Tensor

We propose a generalized quantum geometric tenor to understand topological quantum phase transitions, which can be defined on the parameter space with the adiabatic evolution of a quantum many-body system. The generalized quantum geometric tenor contains two different local measurements, the non-Abelian Riemannian metric and the non-Abelian Berry curvature, which are recognized as two natural geometric characterizations for the change of the ground-state properties when the parameter of the Hamiltonian varies. Our results show the symmetry-breaking and topological quantum phase transitions can…