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We introduce a complete equational theory for the fragment of quantum circuits generated by the real Clifford gates plus the two-qubit controlled-Hadamard gate. That is, we give a simple set of equalities between circuits of this fragment,…

Quantum Physics · Physics 2026-02-09 Alexandre Clément

Quantum machine learning models are designed for performing learning tasks. Some quantum classifier models are proposed to assign classes of inputs based on fidelity measurements. Quantum Hadamard test is a well-known quantum algorithm for…

Quantum Physics · Physics 2025-08-07 Vivek Mehta , Arghya Choudhury , Utpal Roy

In this paper, we extend the protocol of classical verification of quantum computations (CVQC) recently proposed by Mahadev to make the verification efficient. Our result is obtained in the following three steps: $\bullet$ We show that…

Quantum Physics · Physics 2020-03-16 Nai-Hui Chia , Kai-Min Chung , Takashi Yamakawa

The rapid advancement of quantum hardware necessitates the development of reliable methods to certify its correct functioning. However, existing certification tests fall short, as they either suffer from systematic errors or do not…

Quantum Physics · Physics 2025-08-13 Jan Nöller , Nikolai Miklin , Martin Kliesch , Mariami Gachechiladze

The Hadamard test is naturally suited for the intermediate regime between the current era of noisy quantum devices and complete fault tolerance. Its applications use measurements of the auxiliary qubit to extract information, but disregard…

Quantum Physics · Physics 2025-10-21 Paul K. Faehrmann , Jens Eisert , Richard Kueng

In this work we define an universal arithmetical algorithm, by means of the standard quantum mechanical formalism, called universal qm-arithmetical algorithm. By universal qm-arithmetical algorithm any decidable arithmetical formula…

Quantum Physics · Physics 2007-05-23 Vladan Pankovic , Milan Predojevic

We study classical simulation of quantum computation, taking the Gottesman-Knill theorem as a starting point. We show how each Clifford circuit can be reduced to an equivalent, manifestly simulatable circuit (normal form). This provides a…

Quantum Physics · Physics 2012-02-20 M. Van den Nest

We give a careful proof that a parallelized version of adiabatic quantum computation can efficiently simulate universal gate model quantum computation. The proof specifies an explicit parameter-dependent Hamiltonian $H({\lambda})$ that is…

Quantum Physics · Physics 2019-02-20 Ari Mizel

We define a general formulation of quantum PCPs, which captures adaptivity and multiple unentangled provers, and give a detailed construction of the quantum reduction to a local Hamiltonian with a constant promise gap. The reduction turns…

Quantum Physics · Physics 2025-07-16 Harry Buhrman , Jonas Helsen , Jordi Weggemans

Quantum mechanics is widely regarded as a complete theory, yet we argue it is a tractable projection of a deeper, computationally-inaccessible classical variational structure. By analyzing the coupled partial differential equations of the…

General Physics · Physics 2026-01-26 Khaled Mnaymneh

We describe criteria for implementation of quantum computation in qudits. A qudit is a d-dimensional system whose Hilbert space is spanned by states |0>, |1>,... |d-1>. An important earlier work of Mathukrishnan and Stroud [1] describes how…

Quantum Physics · Physics 2009-11-10 Gavin K. Brennen , Dianne P. O'Leary , Stephen S. Bullock

Quantum simulators are engineered devices controllably designed to emulate complex and classically intractable quantum systems. A key challenge is to certify whether the simulator truly mimics the Hamiltonian of interest. This certification…

Quantum Physics · Physics 2020-06-12 Abolfazl Bayat , Benoit Voisin , Gilles Buchs , Joe Salfi , Sven Rogge , Sougato Bose

Recent work has demonstrated the existence of universal Hamiltonians - simple spin lattice models that can simulate any other quantum many body system to any desired level of accuracy. Until now proofs of universality have relied on…

Quantum Physics · Physics 2022-03-18 Tamara Kohler , Stephen Piddock , Johannes Bausch , Toby Cubitt

Watrous had presented the first proof of zero-knowledge property of a proof system against a quantum verifier. The key of the proof is the construction of a quantum simulator. In the construction, the 'failure state' is rotated to the…

Quantum Physics · Physics 2007-05-23 Keiji Matsumoto

Quantum annealing (QA) has the potential to significantly improve solution quality and reduce time complexity in solving combinatorial optimization problems compared to classical optimization methods. However, due to the limited number of…

Quantum Physics · Physics 2025-04-09 Seongmin Kim , Sang-Woo Ahn , In-Saeng Suh , Alexander W. Dowling , Eungkyu Lee , Tengfei Luo

In this work we demonstrate the use of adapted classical phase retrieval algorithms to perform control-free quantum phase estimation. We eliminate the costly controlled time evolution and Hadamard test commonly required to access the…

Given a verifier circuit for a problem in QMA, we show how to exponentially amplify the gap between its acceptance probabilities in the `yes' and `no' cases, with a method that is quadratically faster than the procedure given by Marriott…

Quantum Physics · Physics 2009-08-22 Daniel Nagaj , Pawel Wocjan , Yong Zhang

In a recent breakthrough, Mahadev constructed an interactive protocol that enables a purely classical party to delegate any quantum computation to an untrusted quantum prover. In this work, we show that this same task can in fact be…

Quantum Physics · Physics 2022-02-14 Gorjan Alagic , Andrew M. Childs , Alex B. Grilo , Shih-Han Hung

If we admit that quantum mechanics (QM) is universal theory, then QM should contain also some description of classical mechanical systems. The presented text contains description of two different ways how the mathematical description of…

Mathematical Physics · Physics 2020-07-28 Pavel Bóna

We show that universal quantum computation can be concretely made fault-tolerant without mid-circuit measurements. To this end, we introduce a measurement-free deformation protocol of the Bacon-Shor code to realize a logical $\mathit{CCZ}$…

Quantum Physics · Physics 2025-11-18 Stefano Veroni , Alexandru Paler , Giacomo Giudice