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For secure practical systems, quantum key distribution (QKD) must provide high key rates over long distances. Time-entanglement-based QKD promises to increase the secret key rate and distribution distances compared to other QKD…

Information Theory · Computer Science 2023-03-06 Lara Dolecek , Emina Soljanin

The frequency stability achieved by an optical atomic clock ultimately depends on the coherence of its local oscillator. Even the best ultrastable lasers only allow interrogation times of a few seconds, at present. Here we present a…

Fidelity estimation for entangled states constitutes an essential building block for quality control and error detection in quantum networks. Nonetheless, quantum networks often encounter heterogeneous and correlated noise, leading to…

Quantum Physics · Physics 2024-11-18 Liangzhong Ruan , Bas Dirkse

We analyze the effect of realistic noise sources for an atomic clock consisting of a local oscillator that is actively locked to a spin-squeezed (entangled) ensemble of $N$ atoms. We show that the use of entangled states can lead to an…

Quantum Physics · Physics 2009-11-10 A. Andre , A. S. Sorensen , M. D. Lukin

It was recently shown that an entangled coherent state, which is a superposition of two different coherent states, can surpass the performance of noon state in estimating an unknown phase-shift. This may hint at further enhancement in phase…

Quantum Physics · Physics 2023-07-19 Su-Yong Lee , Chang-Woo Lee , Hyunchul Nha , Dagomir Kaszlikowski

Block-encodings have become one of the most common oracle assumptions in the circuit model. I present an algorithm that uses von Neumann's measurement procedure to measure a phase, using time evolution on a block-encoded Hamiltonian as a…

Quantum Physics · Physics 2025-09-05 S. E. Skelton

Optical lattice clocks (OLCs) are at the forefront of precision metrology, operating near a standard quantum limit (SQL) set by quantum noise. Harnessing quantum entanglement offers a promising route to surpass this limit, yet there remain…

Entanglement lies at the core of quantum algorithms designed to solve problems that are intractable by classical approaches. One such algorithm, quantum annealing (QA), provides a promising path to a practical quantum processor. We have…

Quantum phase estimation is a paradigmatic problem in quantum sensing andmetrology. Here we show that adaptive methods based on classical machinelearning algorithms can be used to enhance the precision of quantum phase estimation when noisy…

Quantum Physics · Physics 2021-09-01 Nelson Filipe Costa , Yasser Omar , Aidar Sultanov , Gheorghe Sorin Paraoanu

It is shown how possible corrections to ordinary quantum mechanics described by the Lindblad equation might be detected by exploiting the great precision of atomic clocks.

Quantum Physics · Physics 2016-11-02 Steven Weinberg

We develop several algorithms for performing quantum phase estimation based on basic measurements and classical post-processing. We present a pedagogical review of quantum phase estimation and simulate the algorithm to numerically determine…

Quantum Physics · Physics 2013-07-30 Krysta M. Svore , Matthew B. Hastings , Michael Freedman

Advancements in physics are often motivated/accompanied by advancements in our precision measurements abilities. The current generation of atomic and optical interferometers is limited by shot noise, a fundamental limit when estimating a…

Quantum Physics · Physics 2014-11-20 Luca Pezze' , Augusto Smerzi

Quantum entanglement has been generated and verified in cold-atom experiments and used to make atom-interferometric measurements below the shot-noise limit. However, current state-of-the-art cold-atom devices exploit separable (i.e.…

Quantum Physics · Physics 2021-04-13 Stuart S. Szigeti , Onur Hosten , Simon A. Haine

Phase clocks are synchronization tools that implement a form of logical time in distributed systems. For systems tolerating transient faults by self-repair of damaged data, phase clocks can enable reasoning about the progress of distributed…

Distributed, Parallel, and Cluster Computing · Computer Science 2007-05-23 Ted Herman

Learning unknown processes affecting a quantum system reveals underlying physical mechanisms and enables suppression, mitigation, and correction of unwanted effects. Describing a general quantum process requires an exponentially large…

Spatial entanglement of quantum states has become a central paradigm of many-body physics. Here, we unearth a fundamentally different form of entanglement, the entanglement between imaginary time scales. This time-scale entanglement is…

While the concept of entanglement purification protocols (EPPs) is straightforward, the integration of EPPs in network architectures requires careful performance evaluations and optimizations that take into account realistic conditions and…

Quantum Physics · Physics 2025-07-14 Allen Zang , Xin-An Chen , Eric Chitambar , Martin Suchara , Tian Zhong

We report an experimental investigation of the role of measurement in quantum metrology when the states of the probes are mixed. In particular, we investigated optimized local measurements and general global projective measurements,…

Quantum Physics · Physics 2021-02-22 R. S. Piera , S. P. Walborn , G. H. Aguilar

There exists, in general, a convex set of quantum state estimators that maximize the likelihood for informationally incomplete data. We propose an estimation scheme, catered to measurement data of this kind, to search for the exact…

High-precision clock synchronization is essential for a wide range of network-distributed applications. In the quantum space, these applications include communication, sensing, and positioning. However, current synchronization techniques…

Quantum Physics · Physics 2025-11-18 Ravi Singh Adhikari , Aman Gupta , Anju Rani , Xiaoyu Ai , Robert Malaney