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We propose a quantum machine learning algorithm for efficiently solving a class of problems encoded in quantum controlled unitary operations. The central physical mechanism of the protocol is the iteration of a quantum time-delayed equation…

Quantum phase estimation is the workhorse behind any quantum algorithm and a promising method for determining ground state energies of strongly correlated quantum systems. Low-cost quantum phase estimation techniques make use of circuits…

Quantum Physics · Physics 2019-03-27 T. E. O'Brien , B. Tarasinski , B. M. Terhal

In this work, we consider biased-noise qubits affected only by bit-flip errors, which is motivated by existing systems of stabilized cat qubits. This property allows us to design a class of noisy Hadamard-tests involving entangling and…

In measurement-based quantum computing an algorithm is performed by measurements on highly-entangled resource states. To date, several implementations were demonstrated, all of them assuming perfect noise-free environments. Here we consider…

Modelling non-linear activation functions on quantum computers is vital for quantum neurons employed in fully quantum neural networks, however, remains a challenging task. We introduce an amplitude-based implementation for approximating…

Quantum Physics · Physics 2023-02-09 Jonas Koppe , Mark-Oliver Wolf

Phase estimation is a quantum algorithm for measuring the eigenvalues of a Hamiltonian. We propose and rigorously analyse a randomized phase estimation algorithm with two distinctive features. First, our algorithm has complexity independent…

Quantum Physics · Physics 2022-08-09 Kianna Wan , Mario Berta , Earl T. Campbell

Quantum-phase-estimation algorithms are critical subroutines in many applications for quantum computers and in quantum-metrology protocols. These algorithms estimate the unknown strength of a unitary evolution. By using coherence or…

Quantum Physics · Physics 2023-03-06 Joseph G. Smith , Crispin H. W. Barnes , David R. M. Arvidsson-Shukur

We consider performing phase estimation under the following conditions: we are given only one copy of the input state, the input state does not have to be an eigenstate of the unitary, and the state must not be measured. Most quantum…

Quantum Physics · Physics 2022-12-13 Patrick Rall

Quantum algorithms are able to solve particular problems exponentially faster than conventional algorithms, when implemented on a quantum computer. However, all demonstrations to date have required already knowing the answer to construct…

Quantum Physics · Physics 2013-03-22 Xiao-Qi Zhou , Pruet Kalasuwan , Timothy C. Ralph , Jeremy L. O'Brien

Quantum algorithms require accurate representations of electronic states on a quantum device, yet the approximation of electronic wave functions for strongly correlated systems remains a profound theoretical challenge, with existing methods…

Quantum Physics · Physics 2025-04-29 Dipanjali Halder , Dibyendu Mondal , Rahul Maitra

We present a method for mitigating measurement errors on quantum computing platforms that does not form the full assignment matrix, or its inverse, and works in a subspace defined by the noisy input bit-strings. This method accommodates…

Quantum Physics · Physics 2021-11-11 Paul D. Nation , Hwajung Kang , Neereja Sundaresan , Jay M. Gambetta

Quantum computing can provide speedups in solving many problems as the evolution of a quantum system is described by a unitary operator in an exponentially large Hilbert space. Such unitary operators change the phase of their eigenstates…

Quantum Physics · Physics 2024-01-23 Youle Wang , Lei Zhang , Zhan Yu , Xin Wang

Quantum phase estimation is a central primitive in quantum algorithms and sensing, where performance is governed by the sensitivity of measurement signals to the target parameter. While existing methods have developed increasingly…

Quantum Physics · Physics 2026-04-02 Zikang Jia , Suying Liu , Yulong Dong

We explore the usefulness of mid-circuit measurements to enhance quantum algorithmics. Specifically, we assess how quantum phase estimation (QPE) and mid-circuit measurements can improve the performance of variational quantum algorithms.…

Quantum Physics · Physics 2025-09-03 Antoine Lemelin , Christophe Pere , Olivier Landon-Cardinal , Camille Coti

Performing experiments on small-scale quantum computers is certainly a challenging endeavor. Many parameters need to be optimized to achieve high-fidelity operations. This can be done efficiently for operations acting on single qubits as…

Quantum Physics · Physics 2016-08-31 M. Müller , A. Rivas , E. A. Martínez , D. Nigg , P. Schindler , T. Monz , R. Blatt , M. A. Martin-Delgado

Quantum effects like entanglement and coherent amplification can be used to drastically enhance the accuracy of quantum parameter estimation beyond classical limits. However, challenges such as decoherence and time-dependent errors hinder…

Quantum Physics · Physics 2025-02-18 Yulong Dong , Jonathan A. Gross , Murphy Yuezhen Niu

In this paper, we introduce an efficient algorithm for the quantum amplitude estimation task which works in noisy intermediate-scale quantum(NISQ) devices. The quantum amplitude estimation is an important problem which has various…

Quantum Physics · Physics 2021-11-29 Kouhei Nakaji

Quantum amplitude amplification and quantum phase estimation are two fundamental quantum algorithms. All known quantum algorithms are derived from these two algorithms. Even the adiabatic quantum algorithms can also be efficiently simulated…

Quantum Physics · Physics 2016-11-11 Avatar Tulsi

An important step in building a quantum computer is calibrating experimentally implemented quantum gates to produce operations that are close to ideal unitaries. The calibration step involves estimating the systematic errors in gates and…

Quantum Physics · Physics 2021-10-22 Shelby Kimmel , Guang Hao Low , Theodore J. Yoder

Quantum error correction and quantum error detection necessitate syndrome measurements to detect errors. Performing syndrome measurements for each stabilizer generator can be a significant overhead, considering the fact that the readout…

Quantum Physics · Physics 2023-10-31 Kento Tsubouchi , Yasunari Suzuki , Yuuki Tokunaga , Nobuyuki Yoshioka , Suguru Endo