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Solving non-Hermitian quantum many-body systems on a quantum computer by minimizing the variational energy is challenging as the energy can be complex. Here, based on energy variance, we propose a variational method for solving the…

Quantum Physics · Physics 2024-02-21 Xu-Dan Xie , Zheng-Yuan Xue , Dan-Bo Zhang

We compare critical quantum sensing to passive quantum strategies to perform frequency estimation, in the case of single-mode quadratic Hamiltonians. We show that, while in the unitary case both strategies achieve precision scaling…

Quantum Physics · Physics 2024-08-07 Uesli Alushi , Wojciech Górecki , Simone Felicetti , Roberto Di Candia

We present a simple but general framework for constructing quantum circuits that implement the multiply-controlled unitary $\text{Select}(H) \equiv \sum_\ell |\ell\rangle\langle\ell|\otimes H_\ell$, where $H = \sum_\ell H_\ell$ is the…

Quantum Physics · Physics 2021-01-14 Kianna Wan

We present a finite-temperature canonical-ensemble determinant quantum Monte Carlo algorithm that enforces an exact fermion number and enables stable simulations of correlated lattice fermions. We propose a stabilized QR update that reduces…

Strongly Correlated Electrons · Physics 2026-01-21 Tu Hong , Kun Chen , Xiao Yan Xu

Simulating many-body fermionic systems in conventional qubit-based quantum computers poses significant challenges due to the overheads associated with the encoding of fermionic statistics in qubits, leading to the proposal of native…

Quantum Physics · Physics 2025-12-15 Ahana Ghoshal , Carlos de Gois , Kiara Hansenne , Otfried Gühne , Hai-Chau Nguyen

Chiral superconductors have the ability to host topologically protected Majorana zero modes which have been proposed as future qubits for topological quantum computing. The recently introduced magnet--superconductor hybrid (MSH) systems…

Mesoscale and Nanoscale Physics · Physics 2019-11-27 Eric Mascot , Sagen Cocklin , Stephan Rachel , Dirk K. Morr

In these notes, we review the main results of our approach to fermion masses. The marge mass ratios between fermions, confronted with a unique breaking mechanism leading to vector bosons masses, led us to consider the possibility that they…

High Energy Physics - Phenomenology · Physics 2014-09-30 J-M Frère , M Libanov , S Mollet , S Troitsky

For a non-Hermitian Hamiltonian H possessing a real spectrum, we introduce a canonical orthonormal basis in which a previously introduced unitary mapping of H to a Hermitian Hamiltonian h takes a simple form. We use this basis to construct…

Quantum Physics · Physics 2011-07-19 Ali Mostafazadeh , Ahmet Batal

We present a procedure for exactly diagonalizing finite-range quadratic fermionic Hamiltonians with arbitrary boundary conditions in one of D dimensions, and periodic in the remaining D-1. The key is a Hamiltonian-dependent separation of…

Superconductivity · Physics 2016-10-27 Abhijeet Alase , Emilio Cobanera , Gerardo Ortiz , Lorenza Viola

To obtain estimates of electronic energies, the Variational Quantum Eigensolver (VQE) technique performs separate measurements for multiple parts of the system Hamiltonian. Current quantum hardware is restricted to projective single-qubit…

Quantum Physics · Physics 2019-10-22 Artur F. Izmaylov , Tzu-Ching Yen , Robert A. Lang , Vladyslav Verteletskyi

To measure an observable of a quantum mechanical system leaves it in one of its eigenstates and the result of the measurement is one of its eigenvalues. This process is shown to be a computational resource. It allows one, in principle, to…

Quantum Physics · Physics 2009-11-06 Stefan Weigert

We present an extension of the Evolving density matrices on Qubits (E$\rho$OQ) framework that enables efficient fault-tolerant preparation of fermionic quantum states. The original method circumvents state preparation by stochastic…

Quantum Physics · Physics 2026-03-25 Erik J. Gustafson , Henry Lamm

The problem of how measurement in quantum mechanics takes place has existed since its formulation. Von Neumann proposed a scheme where he treated measurement as a two-part process -- a unitary evolution in the full system-ancilla space and…

Quantum Physics · Physics 2023-12-14 Gurpahul Singh , Ritesh K. Singh , Soumitro Banerjee

Polynomially-large ground-state energy gaps are rare in many-body quantum systems, but useful for adiabatic quantum computing. We show analytically that the gap is generically polynomially-large for quadratic fermionic Hamiltonians. We then…

Quantum Physics · Physics 2013-05-29 Michael J. O'Hara , Dianne P. O'Leary

Many-body entanglement is studied within the algebraic approach to quantum physics in systems made of Majorana fermions. In this framework, the notion of separability stems from partitions of the algebra of observables and properties of the…

Quantum Physics · Physics 2016-07-20 F. Benatti , R. Floreanini

We present explicit expressions for the central piece of a variational method developed by Shi et al. which extends variational wave functions that are efficiently computable on classical computers beyond mean-field to generalized Gaussian…

Quantum Physics · Physics 2021-09-23 Michael P. Kaicher , Simon B. Jäger , Frank K. Wilhelm

Fermionic atoms in optical lattices provide a native implementation of Fermi-Hubbard (FH) models that can be used as analog quantum simulators of many-body fermionic systems. Recent experimental advances include the time-dependent local…

Utilizing the sparsity of the electronic structure problem, fragmentation methods have been researched for decades with great success, pushing the limits of ab initio quantum chemistry ever further. Recently, this set of methods was…

Chemical Physics · Physics 2024-12-03 Marco Bauer , Andreas Dreuw , Anthony D. Dutoi

Quantum symmetrization is the task of transforming a non-strictly increasing list of $n$ integers into an equal superposition of all permutations of the list (or more generally, performing this operation coherently on a superposition of…

Quantum Physics · Physics 2025-05-06 Zhenning Liu , Andrew M. Childs , Daniel Gottesman

A new method is introduced for probing Topological Superconductors. The integration of the superconding fermions generates a topological $\mathbf{Chern-Simons}$ sound action . Dislocations induce Majorana zero modes inside the sample,…

Superconductivity · Physics 2015-01-27 D. Schmeltzer