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Over the past decade classical optical systems with gain or loss, modelled by non-Hermitian parity-time symmetric Hamiltonians, have been deeply investigated. Yet, their applicability to the quantum domain with number-resolved photonic…

Quantum Physics · Physics 2024-05-15 Ross Wakefield , Anthony Laing , Yogesh N. Joglekar

We provide a new approach for compiling quantum simulation circuits that appear in Trotter, qDRIFT and multi-product formulas to Clifford and non-Clifford operations that can reduce the number of non-Clifford operations by a factor of up to…

Quantum Physics · Physics 2023-05-09 Priyanka Mukhopadhyay , Nathan Wiebe , Hong Tao Zhang

Gaussian unitary transformations are generated by quadratic Hamiltonians, i.e., Hamiltonians containing quadratic terms in creations and annihilation operators, and are heavily used in many areas of quantum physics, ranging from quantum…

Quantum Physics · Physics 2024-09-19 Tommaso Guaita , Lucas Hackl , Thomas Quella

Combining non-hermiticity and interactions yields novel effects in open quantum many-body systems. Here, we develop the generalized Schrieffer-Wolff transformation and derive the effective Hamiltonian suitable for various quasi-degenerate…

Quantum Physics · Physics 2024-02-13 Grigory A. Starkov , Mikhail V. Fistul , Ilya M. Eremin

Open classical and quantum systems with effective parity-time ($\mathcal{PT}$) symmetry, over the past five years, have shown tremendous promise for advances in lasers, sensing, and non-reciprocal devices. And yet, how such effective…

Quantum Physics · Physics 2020-10-21 Archak Purkayastha , Manas Kulkarni , Yogesh N. Joglekar

Preserving spin symmetry in variational quantum algorithms is essential for producing physically meaningful electronic wavefunctions. Implementing spin-adapted transformations on quantum hardware, however, is challenging because the…

Quantum Physics · Physics 2026-05-04 Paarth Jain , Artur F. Izmaylov , Erik R. Kjellgren

The effective Hamiltonian serves as the conceptual pivot of quantum engineering, transforming physical complexity into programmable logic; yet, its construction remains compromised by the mathematical non-uniqueness of block…

Quantum Physics · Physics 2026-02-04 Hao-Yu Guan , Xiao-Long Zhu , Yu-Hang Dang , Xiu-Hao Deng

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

Unitary transformations are the fundamental building blocks of gates and operations in quantum information processing allowing the complete manipulation of quantum systems in a coherent manner. In the case of photons, optical elements that…

Quantum Physics · Physics 2020-01-30 Florian Brandt , Markus Hiekkamäki , Frédéric Bouchard , Marcus Huber , Robert Fickler

We discuss encodings of fermionic many-body systems by qubits in the presence of symmetries. Such encodings eliminate redundant degrees of freedom in a way that preserves a simple structure of the system Hamiltonian enabling quantum…

Quantum Physics · Physics 2017-01-31 Sergey Bravyi , Jay M. Gambetta , Antonio Mezzacapo , Kristan Temme

Parity-time ($PT$)-symmetric Hamiltonians exhibit non-unitary dynamical evolution while maintaining real spectra, and offer unique approaches to quantum sensing and entanglement generation. Here we present a method for simulating the…

Quantum Physics · Physics 2026-01-15 Maryam Abbasi , Koray Aydogan , Anthony W. Schlimgen , Kade Head-Marsden

The quantum Fourier transform (QFT) is a fundamental primitive in quantum computation and quantum information. In this work, we generalize the QFT for finite groups to a QFT for finite-dimensional semisimple algebras, and give efficient…

Quantum Physics · Physics 2026-05-08 Ben Foxman , Barak Nehoran , Yongshan Ding

Exploiting inherent symmetries is a common and effective approach to speed up the simulation of quantum systems. However, efficiently accounting for non-Abelian symmetries, such as the $SU(2)$ total-spin symmetry, remains a major challenge.…

Quantum Physics · Physics 2024-12-20 Anthony Gandon , Alberto Baiardi , Max Rossmannek , Werner Dobrautz , Ivano Tavernelli

The special unitary group SU(2) plays a fundamental role in the description of symmetries in quantum mechanics, theoretical physics, and spherical signal processing. In this paper, we address the computational challenges of performing…

Computational Physics · Physics 2026-05-26 Julio Delgado , Alejandro Umaña

This paper introduces an innovative approach for representing Gaussian fermionic states, pivotal in quantum spin systems and fermionic models, within a range of alternative quantum bases. We focus on transitioning these states from the…

Quantum Physics · Physics 2024-06-24 Babak Tarighi , Reyhaneh Khasseh , M. A. Rajabpour

We propose a method for the realization of the two-qubit quantum Fourier transform (QFT) using a Hamiltonian which possesses the circulant symmetry. Importantly, the eigenvectors of the circulant matrices are the Fourier modes and do not…

Quantum Physics · Physics 2020-01-28 Peter A. Ivanov , Nikolay V. Vitanov

We present an efficient quantum circuit for block encoding pairing Hamiltonian often studied in nuclear physics. Our block encoding scheme does not require mapping the creation and annihilation operators to the Pauli operators and…

Nuclear Theory · Physics 2024-02-22 Diyi Liu , Weijie Du , Lin Lin , James P. Vary , Chao Yang

Quantum chemistry and materials science are among the most promising areas for demonstrating algorithmic quantum advantage and quantum utility due to their inherent quantum mechanical nature. Still, large-scale simulations of quantum…

Efficiently calculating the low-lying eigenvalues of Hamiltonians, written as sums of Pauli operators, is a fundamental challenge in quantum computing. While various methods have been proposed to reduce the complexity of quantum circuits…

Quantum Physics · Physics 2025-08-08 Abhinav Anand , Kenneth R. Brown

A gauge invariant mathematical formalism based on deformation quantization is outlined to model an $\mathcal{N}=2$ supersymmetric system of a spin $1/2$ charged particle placed in a nocommutative plane under the influence of a vertical…

Mathematical Physics · Physics 2024-07-02 Md. Rafsanjany Jim , S. Hasibul Hassan Chowdhury
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