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We consider stability and uniqueness in real phase retrieval problems over general input sets. Specifically, we assume the data consists of noisy quadratic measurements of an unknown input x in R^n that lies in a general set T and study…

Information Theory · Computer Science 2012-11-06 Yonina C. Eldar , Shahar Mendelson

For parameter estimation from an $N$-component composite quantum system, it is known that a separable preparation leads to a mean-squared estimation error scaling as $1/N$ while an entangled preparation can in some conditions afford a…

Quantum Physics · Physics 2019-04-04 Francois Chapeau-Blondeau

Recent studies have been spurred on by the promise of advanced quantum computing technology, which has led to the development of quantum computer simulations on classical hardware. Grover's quantum search algorithm is one of the well-known…

We consider stability of a general quantum algorithm with respect to a fixed but unknown residual interaction between qubits, and show a surprising fact, namely that the average fidelity of quantum computation increases by decreasing…

Quantum Physics · Physics 2009-11-07 Tomaz Prosen , Marko Znidaric

Quantum state purification, a process that aims to recover a state closer to a system's principal eigenstate from multiple copies of an unknown noisy quantum state, is crucial for restoring noisy states to a more useful form in quantum…

Quantum Physics · Physics 2025-09-25 Keming He , Chengkai Zhu , Hongshun Yao , Jinguo Liu , Yinan Li , Xin Wang

Quantum searching for one of $N$ marked items in an unsorted database of $n$ items is solved in $\mathcal{O}(\sqrt{n/N})$ steps using Grover's algorithm. Using nonlinear quantum dynamics with a Gross-Pitaevskii type quadratic nonlinearity,…

Quantum Physics · Physics 2017-12-12 K. de Lacy , L. Noakes

We investigate the dynamics of entanglement and quantum discord of two qubits in liquid state homonuclear NMR. Applying a phenomenological description for NMR under relaxation process, and taking a group of typical parameters of NMR, we…

Quantum Physics · Physics 2011-06-02 Jianwei Xu , Qihui Chen

Achieving a practical advantage with near-term quantum computers hinges on having effective methods to suppress errors. Recent breakthroughs have introduced methods capable of exponentially suppressing errors by preparing multiple noisy…

Quantum Physics · Physics 2021-03-26 Piotr Czarnik , Andrew Arrasmith , Lukasz Cincio , Patrick J. Coles

The Traveling Salesman Problem (TSP) is a classical NP-hard problem that plays a crucial role in combinatorial optimization. In this paper, we are interested in the quantum search framework for the TSP because it has robust theoretical…

Quantum Physics · Physics 2025-04-25 Bai Xujun , Shang Yun

We give a pair of algorithms that efficiently learn a quantum state prepared by Clifford gates and $O(\log n)$ non-Clifford gates. Specifically, for an $n$-qubit state $|\psi\rangle$ prepared with at most $t$ non-Clifford gates, our…

Quantum Physics · Physics 2025-11-07 Sabee Grewal , Vishnu Iyer , William Kretschmer , Daniel Liang

The rapid development of machine learning and quantum computing has placed quantum machine learning at the forefront of research. However, existing quantum machine learning algorithms based on quantum variational algorithms face challenges…

Quantum Physics · Physics 2025-08-22 Da Zhang , Xin Li , Yibin Guo , Haifeng Yu , Yirong Jin , Zhang-Qi Yin

We show that a quantum computer operating with a small number of qubits can simulate the dynamical localization of classical chaos in a system described by the quantum sawtooth map model. The dynamics of the system is computed efficiently…

Quantum Physics · Physics 2007-05-23 Giuliano Benenti , Giulio Casati , Simone Montangero , Dima L. Shepelyansky

In classical computation, a problem can be solved in multiple steps where calculated results of each step can be copied and used repeatedly. While in quantum computation, it is difficult to realize a similar multi-step computation process…

Quantum Physics · Physics 2023-01-19 Hefeng Wang , Sixia Yu , Hua Xiang

Quantum state tomography is the problem of estimating a given quantum state. Usually, it is required to run the quantum experiment - state preparation, state evolution, measurement - several times to be able to estimate the output quantum…

General Physics · Physics 2025-04-30 Shibdas Roy , Filippo Caruso , Srushti Patil , Anumita Mukhopadhyay

We use a Bayesian approach to optimally solve problems in noisy binary search. We deal with two variants: 1. Each comparison can be erroneous with some probability $1 - p$. 2. At each stage $k$ comparisons can be performed in parallel and a…

Quantum Physics · Physics 2011-11-09 M. Ben-Or , Avinatan Hassidim

With a combination of the quantum repeater and the cluster state approaches, we show that efficient quantum computation can be constructed even if all the entangling quantum gates only succeed with an arbitrarily small probability $p$. The…

Quantum Physics · Physics 2009-11-11 L. -M. Duan , R. Raussendorf

The quantum adiabatic unstructured search algorithm is one of only a handful of quantum adiabatic optimization algorithms to exhibit provable speedups over their classical counterparts. With no fault tolerance theorems to guarantee the…

Quantum Physics · Physics 2019-11-14 Mikhail Slutskii , Tameem Albash , Lev Barash , Itay Hen

Quantum error-correction codes would protect an arbitrary state of a multi-qubit register against decoherence-induced errors, but their implementation is an outstanding challenge for the development of large-scale quantum computers. A first…

Grover's Search algorithm was a breakthrough at the time it was introduced, and its underlying procedure of amplitude amplification has been a building block of many other algorithms and patterns for extracting information encoded in…

Quantum Physics · Physics 2020-05-27 Austin Gilliam , Marco Pistoia , Constantin Gonciulea

Low-frequency noise presents a serious source of decoherence in solid-state qubits. When combined with a continuous weak measurement of the eigenstates, the low-frequency noise induces a second-order relaxation between the qubit states.…

Quantum Physics · Physics 2011-07-26 L. Tian