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We give a convergent hierarchy of SDP certificates for bounding the spectral gap of local qubit Hamiltonians from below. Our approach is based on the NPA hierarchy applied to a polynomially-sized system of constraints defining the universal…

Quantum Physics · Physics 2025-10-10 Sujit Rao

We study the complexity of quantum query algorithms that make p queries in parallel in each timestep. This model is in part motivated by the fact that decoherence times of qubits are typically small, so it makes sense to parallelize quantum…

Quantum Physics · Physics 2015-02-24 Stacey Jeffery , Frederic Magniez , Ronald de Wolf

The Ground-state criticality of many-body systems is a resource for quantum-enhanced sensing, namely the Heisenberg precision limit, provided that one has access to the whole system. We show that for partial accessibility, the sensing…

Quantum Physics · Physics 2021-11-29 Utkarsh Mishra , Abolfazl Bayat

Quantum adiabatic optimization seeks to solve combinatorial problems using quantum dynamics, requiring the Hamiltonian of the system to align with the problem of interest. However, these Hamiltonians are often incompatible with the native…

We determine the complexity of several constraint satisfaction problems using the quantum adiabatic algorithm in its simplest implementation. We do so by studying the size dependence of the gap to the first excited state of "typical"…

Statistical Mechanics · Physics 2015-03-19 Itay Hen , A. P. Young

This paper argues that the requirement of applicableness of quantum linearity to any physical level from molecules and atoms to the level of macroscopic extensional world, which leads to a main foundational problem in quantum theory…

Quantum Physics · Physics 2014-06-25 Arkady Bolotin

We define a map from an arbitrary quantum circuit to a local Hamiltonian whose ground state encodes the quantum computation. All previous maps relied on the Feynman-Kitaev construction, which introduces an ancillary `clock register' to…

Quantum Physics · Physics 2024-08-08 Anurag Anshu , Nikolas P. Breuckmann , Quynh T. Nguyen

The canonical analysis and subsequent quantization of the (2+1)-dimensional action of pure gravity plus a cosmological constant term is considered, under the assumption of the existence of one spacelike Killing vector field. The proper…

General Relativity and Quantum Cosmology · Physics 2009-01-07 T. Christodoulakis , G. Doulis , Petros A Terzis , E. Melas , Th. Grammenos , G. O. Papadopoulos , A. Spanou

We demonstrate the possibility of (sub)exponential quantum speedup via a quantum algorithm that follows an adiabatic path of a gapped Hamiltonian with no sign problem. This strengthens the superpolynomial separation recently proved by…

Quantum Physics · Physics 2020-11-20 András Gilyén , Umesh Vazirani

We describe an efficient approximation algorithm for evaluating the ground-state energy of the classical Ising Hamiltonian with linear terms on an arbitrary planar graph. The running time of the algorithm grows linearly with the number of…

Quantum Physics · Physics 2009-09-16 Nikhil Bansal , Sergey Bravyi , Barbara M. Terhal

In adiabatic quantum computing finding the dependence of the gap of the Hamiltonian as a function of the parameter varied during the adiabatic sweep is crucial in order to optimize the speed of the computation. Inspired by this challenge,…

Quantum Physics · Physics 2023-06-14 Naeimeh Mohseni , Carlos Navarrete-Benlloch , Tim Byrnes , Florian Marquardt

This work develops a symplectic framework for quantum computing to be applied to classical Hamiltonian systems, exploiting the intrinsic geometric compatibility between unitary quantum evolution and symplectic phase-space dynamics in a…

The demonstration and use of nonlocality, as defined by Bell's theorem, rely strongly on dealing with non-detection events due to losses and detector inefficiencies. Otherwise, the so-called detection loophole could be exploited. The only…

Quantum Physics · Physics 2016-01-20 Gilles Pütz , Nicolas Gisin

This paper considers Hamiltonian identification for a controllable quantum system with non-degenerate transitions and a known initial state. We assume to have at our disposal a single scalar control input and the population measure of only…

Quantum Physics · Physics 2013-04-16 Zaki Leghtas , Gabriel Turinici , Herschel Rabitz , Pierre Rouchon

Different candidates of Quantum Gravity such as String Theory, Doubly Special Relativity, Loop Quantum Gravity and black hole physics all predict the existence of a minimum observable length or a maximum observable momentum which modifies…

High Energy Physics - Theory · Physics 2010-11-30 Pouria Pedram

Quantum query complexity is known to be characterized by the so-called quantum adversary bound. While this result has been proved in the standard discrete-time model of quantum computation, it also holds for continuous-time (or…

Quantum Physics · Physics 2015-07-01 Mathieu Brandeho , Jérémie Roland

Pivotal within quantum physics, the concept of quantum incompatibility is generally related to algebraic aspects of the formalism, such as commutation relations and unbiasedness of bases. Recently, the concept was identified as a resource…

Quantum Physics · Physics 2020-12-24 E. Martins , M. F. Savi , R. M. Angelo

We present a complete quantization of an approximately homogeneous and isotropic universe with small scalar perturbations. We consider the case in which the matter content is a minimally coupled scalar field and the spatial sections are…

General Relativity and Quantum Cosmology · Physics 2013-10-16 Mikel Fernández-Méndez , Guillermo A. Mena Marugán , Javier Olmedo

Hamiltonian quantum simulation of bosons on digital quantum computers requires truncating the Hilbert space to finite dimensions. The method of truncation and the choice of basis states can significantly impact the complexity of the quantum…

Quantum Physics · Physics 2025-10-10 Masanori Hanada , Shunji Matsuura , Emanuele Mendicelli , Enrico Rinaldi

There are many reasons to believe that there is a fundamental minimum length scale below which distances cannot be reliably resolved. One method of constructing a quantum field with a finite minimum length scale is to use bandlimited…

Quantum Physics · Physics 2020-12-24 Laura J. Henderson , Nicolas C. Menicucci
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