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Overcoming the influence of noise and imperfections in quantum devices is one of the main challenges for viable quantum applications. In this article, we present different protocols, which we denote as "superposed quantum error mitigation",…

Many fundamental properties of a quantum system are captured by its Hamiltonian and ground state. Despite the significance of ground states preparation (GSP), this task is classically intractable for large-scale Hamiltonians. Quantum neural…

Quantum Physics · Physics 2023-04-11 Xinbiao Wang , Junyu Liu , Tongliang Liu , Yong Luo , Yuxuan Du , Dacheng Tao

In recent years, quantum algorithms have been proposed which use quantum phase estimation (QPE) coherently as a subroutine without measurement. In order to do this effectively, the routine must be able to distinguish eigenstates with…

Quantum Physics · Physics 2024-04-19 Sean Greenaway , William Pol , Sukin Sim

Statistically interpretable axioms are formulated that define a quantum stochastic process (QSP) as a causally ordered operator field in an arbitrary space-time region T of an open quantum system under a sequential observation at a discrete…

Probability · Mathematics 2007-05-23 V. P. Belavkin

Quantum state tomography (QST) represents an essential tool for the characterization, verification, and validation (QCVV) of quantum processors. Only for a few idealized scenarios, there are analytic results for the optimal measurement set…

Quantum Physics · Physics 2022-12-27 Violeta N. Ivanova-Rohling , Niklas Rohling , Guido Burkard

We describe a method for achieving arbitrary 1-qubit gates and controlled-NOT gates within the context of the Single Cooper Pair Box (SCB) approach to quantum computing. Such gates are sufficient to support universal quantum computation.…

Quantum Physics · Physics 2007-05-23 P. Echternach , C. P. Williams , S. C. Dultz , P. Delsing , S. L. Braunstein , J. P. Dowling

Pure quantum states are often approximately encoded as classical bit strings such as those representing probability amplitudes and those describing circuits that generate the quantum states. The crucial quantity is the minimum length of…

Quantum Physics · Physics 2022-02-04 Seiseki Akibue , Go Kato , Seiichiro Tani

The field of quantum computation currently lacks a formal proof of experimental feasibility. Qubits are fragile and sophisticated quantum error correction is required to achieve reliable quantum computation. The surface code is a promising…

Quantum Physics · Physics 2012-12-04 Austin G. Fowler

In the paper, we consider quantum circuits for the Quantum Fourier Transform (QFT) algorithm. The QFT algorithm is a very popular technique used in many quantum algorithms. We present a generic method for constructing quantum circuits for…

Quantum Physics · Physics 2026-01-05 Kamil Khadiev , Aliya Khadieva , Vadim Sagitov , Kamil Khasanov

A single-qubit circuit can approximate any bounded complex function stored in the degrees of freedom defining its quantum gates. The single-qubit approximant presented in this work is operated through a series of gates that take as their…

Flexible characterization techniques that identify and quantify experimental imperfections under realistic assumptions are crucial for the development of quantum computers. Gate set tomography is a characterization approach that…

Quantum Physics · Physics 2023-03-31 Raphael Brieger , Ingo Roth , Martin Kliesch

In recent years, the quantum computing community has seen an explosion of novel methods to implement non-trivial quantum computations on near-term hardware. An important direction of research has been to decompose an arbitrary entangled…

Quantum Physics · Physics 2021-11-24 Harsha Nagarajan , Owen Lockwood , Carleton Coffrin

We apply the method of compressed sensing (CS) quantum process tomography (QPT) to characterize quantum gates based on superconducting Xmon and phase qubits. Using experimental data for a two-qubit controlled-Z gate, we obtain an estimate…

We propose a new implementation of a universal set of one- and two-qubit gates for quantum computation using the spin states of coupled single-electron quantum dots. Desired operations are effected by the gating of the tunneling barrier…

Mesoscale and Nanoscale Physics · Physics 2009-10-30 Daniel Loss , David P. DiVincenzo

Quantum systems of infinite dimension, such as bosonic oscillators, provide vast resources for quantum sensing. Yet, a general theory on how to manipulate such bosonic modes for sensing beyond parameter estimation is unknown. We present a…

Quantum Physics · Physics 2024-07-31 Jasmine Sinanan-Singh , Gabriel L. Mintzer , Isaac L. Chuang , Yuan Liu

Many researchers have been heavily investigated on quantum phase estimation (QPE) algorithms to find the unknown phase, since QPE is the core building block of the most quantum algorithms such as the Shor's factoring algorithm, quantum…

Quantum Physics · Physics 2019-03-19 Hamed Mohammadbagherpoor , Young-Hyun Oh , Anand Singh , Xianqing Yu , Andy J. Rindos

Quantum computing is seeking to realize hardware-optimized algorithms for application-related computational tasks. NP (nondeterministic-polynomial-time) is a complexity class containing many important but intractable problems like the…

Quantum Physics · Physics 2021-08-27 Aonan Zhang , Hao Zhan , Junjie Liao , Kaimin Zheng , Tao Jiang , Minghao Mi , Penghui Yao , Lijian Zhang

One of the simplest security proofs of quantum key distribution is based on the so-called complementarity scenario, which involves the complementarity control of an actual protocol and a virtual protocol [M. Koashi, e-print arXiv:0704.3661…

Quantum Physics · Physics 2015-05-18 Kiyoshi Tamaki , Go Kato

The ability to implement the Quantum Fourier Transform (QFT) efficiently on a quantum computer facilitates the advantages offered by a variety of fundamental quantum algorithms, such as those for integer factoring, computing discrete…

Quantum Physics · Physics 2020-04-09 Yunseong Nam , Yuan Su , Dmitri Maslov

Quantum key distribution (QKD) allows for secure communications safe against attacks by quantum computers. QKD protocols are performed by sending a sizeable, but finite, number of quantum signals between the distant parties involved. Many…

Quantum Physics · Physics 2021-01-05 Darius Bunandar , Luke C. G. Govia , Hari Krovi , Dirk R. Englund