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A unitarily invariant projective framework is introduced to analyze the complexity of path-following methods for the eigenvalue problem. A condition number, and its relation to the distance to ill-posedness, is given. A Newton map…

Numerical Analysis · Mathematics 2013-05-27 Diego Armentano

We propose a method for quantum state transfer in spin chains using an adiabatic passage technique. Modifying even and odd nearest-neighbour couplings in time allows to achieve transfer fidelities arbitrarily close to one, without the need…

Quantum Physics · Physics 2007-06-13 K. Eckert , O. Romero-Isart , A. Sanpera

Adiabaticity occurs when, during its evolution, a physical system remains in the instantaneous eigenstate of the hamiltonian. Unfortunately, existing results, such as the quantum adiabatic theorem based on a slow down evolution (H(epsilon…

Quantum Physics · Physics 2009-06-25 Daniel Comparat

Using a recently constructed ensemble of hard 2SAT realizations, that has a unique ground-state we calculate for the quantized theory the median gap correlation length values $\xi_{GAP}$ along the direction of the quantum adiabatic control…

Quantum Physics · Physics 2014-12-18 Neuhaus Thomas

We propose a novel method to sequentially optimize arbitrary single-qubit gates in parameterized quantum circuits for simulating real and imaginary time evolution. The method utilizes full degrees of freedom of single-qubit gates and…

We introduce a family of Hamiltonian systems for measurement-based quantum computation with continuous variables. The Hamiltonians (i) are quadratic, and therefore two body, (ii) are of short range, (iii) are frustration-free, and (iv)…

Quantum Physics · Physics 2011-03-01 Leandro Aolita , Augusto J. Roncaglia , Alessandro Ferraro , Antonio Acín

When solving the Hamiltonian path problem it seems natural to be given additional precedence constraints for the order in which the vertices are visited. For example one could decide whether a Hamiltonian path exists for a fixed starting…

Discrete Mathematics · Computer Science 2025-02-28 Jesse Beisegel , Fabienne Ratajczak , Robert Scheffler

We introduce a simple protocol for measuring properties of a gapped ground state with essentially no disturbance to the state. The required Hamiltonian evolution time scales inversely with the spectral gap and target precision (up to…

Quantum Physics · Physics 2025-12-12 Chi-Fang Chen , Robbie King

We use elementary variational arguments to prove, and improve on, gap estimates which arise in simulating quantum circuits by adiabatic evolution.

Quantum Physics · Physics 2009-01-14 Percy Deift , Mary Beth Ruskai , Wolfgang Spitzer

In adiabatic quantum annealing, the speed with which an anneal can be run, while still achieving a high final ground state fidelity, is dictated by the size of the minimum gap that appears between the ground and first excited state in the…

Quantum Physics · Physics 2024-02-22 Natasha Feinstein , Ivan Shalashilin , Sougato Bose , Paul Warburton

Gibbs state preparation is an important subroutine in quantum computing. In this work we use the detectability lemma to improve Gibbs state preparation. Specifically, we design new Gibbs state preparation methods that do not rely on…

Quantum Physics · Physics 2026-04-09 Di Fang , Jianfeng Lu , Yu Tong , Chu Zhao

We introduce and study the adiabatic dynamics of free-fermion models subject to a local Lindblad bath and in the presence of a time-dependent Hamiltonian. The merit of these models is that they can be solved exactly, and will help us to…

Quantum Physics · Physics 2017-11-20 Maximilian Keck , Simone Montangero , Giuseppe E. Santoro , Rosario Fazio , Davide Rossini

Adiabatic quantum optimization is a procedure to solve a vast class of optimization problems by slowly changing the Hamiltonian of a quantum system. The evolution time necessary for the algorithm to be successful scales inversely with the…

Quantum Physics · Physics 2015-12-16 Salvatore Mandrà , Gian Giacomo Guerreschi , Alán Aspuru-Guzik

An adiabatic change of parameters along a closed path may interchange the (quasi-)eigenenergies and eigenspaces of a closed quantum system. Such discrepancies induced by adiabatic cycles are refereed to as the exotic quantum holonomy, which…

Quantum Physics · Physics 2016-01-05 Atushi Tanaka , Taksu Cheon

A new and intuitive perturbative approach to time-dependent quantum mechanics problems is presented, which is useful in situations where the evolution of the Hamiltonian is slow. The state of a system which starts in an instantaneous…

Quantum Physics · Physics 2009-11-11 R. MacKenzie , E. Marcotte , H. Paquette

We present a deterministic (1+sqrt(5))/2-approximation algorithm for the s-t path TSP for an arbitrary metric. Given a symmetric metric cost on n vertices including two prespecified endpoints, the problem is to find a shortest Hamiltonian…

Data Structures and Algorithms · Computer Science 2011-11-03 Hyung-Chan An , Robert Kleinberg , David B. Shmoys

We introduce an algorithm to perform an optimal adiabatic evolution that operates without an apriori knowledge of the system spectrum. By probing the system gap locally, the algorithm maximizes the evolution speed, thus minimizing the total…

Quantum Physics · Physics 2011-05-10 J. Nehrkorn , S. Montangero , A. Ekert , A. Smerzi , R. Fazio , T. Calarco

A quantum system will stay near its instantaneous ground state if the Hamiltonian that governs its evolution varies slowly enough. This quantum adiabatic behavior is the basis of a new class of algorithms for quantum computing. We test one…

Quantum Physics · Physics 2009-11-07 Edward Farhi , Jeffrey Goldstone , Sam Gutmann , Joshua Lapan , Andrew Lundgren , Daniel Preda

We introduce an architecture for variational quantum algorithms that can be efficiently trained via parameter updates along exact geodesics on the Riemannian state manifold. This features a parameter-optimal circuit ansatz which supersedes…

Transition amplitudes between instantaneous eigenstates of quantum two-level system are evaluated analytically on the basis of a new parametrization of its evolution operator, which has recently been proposed to construct exact solutions.…

Quantum Physics · Physics 2018-03-28 Takayuki Suzuki , Hiromichi Nakazato , Roberto Grimaudo , Antonino Messina