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We establish the conditions under which scalable spin squeezing can be achieved in interacting spin ensembles embedded in arbitrary, inhomogeneous graph geometries. We identify two different forms of squeezing: OAT-like scalable squeezing…

Quantum Physics · Physics 2026-05-26 Andrea Solfanelli , Augusto Smerzi , Peter Zoller , Nicolò Defenu

Variational quantum algorithms (VQAs) face an inherent trade-off between expressivity and trainability: deeper circuits can represent richer states but suffer from noise accumulation and barren plateaus, while shallow circuits remain…

Quantum Physics · Physics 2025-10-31 Shaojun Wu , Shan Jin , Abolfazl Bayat , Xiaoting Wang

Quantum metrology aims to exploit many-body quantum states to achieve parameter-estimation precision beyond the standard quantum limit. For unitary parameter encoding generated by local Hamiltonians, such enhancement is characterized by…

Quantum Physics · Physics 2025-12-24 Junjie Chen , Rui Luo , Yuxuan Yan , You Zhou , Xiongfeng Ma

Two level quantum mechanical systems like spin 1/2 particles lend themselves as a natural qubit implementation. However, encoding a single qubit in several spins reduces the resources necessary for qubit control and can protect from…

Mesoscale and Nanoscale Physics · Physics 2016-06-08 Pascal Cerfontaine , Tim Botzem , Simon Sebastian Humpohl , Dieter Schuh , Dominique Bougeard , Hendrik Bluhm

High-fidelity control of quantum bits is paramount for the reliable execution of quantum algorithms and for achieving fault-tolerance, the ability to correct errors faster than they occur. The central requirement for fault-tolerance is…

We investigate the fidelity of the measurement-based quantum computation (MBQC) when it is coupled with boson environment, by measuring cluster state fidelity and gate fidelity. Two different schemes of cluster state preparation are…

Quantum Physics · Physics 2014-11-25 Jian Wang , Ding Zhong , Liangzhu Mu , Heng Fan

In the field of quantum metrology and sensing, a collection of quantum systems (e.g. spins) are used as a probe to estimate some physical parameter (e.g. magnetic field). It is usually assumed that there are no interactions between the…

Quantum Physics · Physics 2018-05-16 Shane Dooley , Michael Hanks , Shojun Nakayama , William J. Munro , Kae Nemoto

Variational quantum algorithms (VQAs) are increasingly being applied in simulations of strongly-bound (covalently bonded) systems using full molecular orbital basis representations. The application of quantum computers to the weakly-bound…

We construct a universal set of high fidelity quantum gates to be used on a sparse bipartite lattice with always-on Ising couplings. The gates are based on dynamical decoupling sequences using shaped pulses, they protect against…

Quantum Physics · Physics 2013-03-05 Amrit De , Leonid P. Pryadko

Measurement-based entanglement is a method for entangling quantum systems through the state projection that accompanies a parity measurement. We derive a stochastic master equation describing measurement-based entanglement of a pair of…

Quantum Physics · Physics 2024-07-17 Remy L. Delva , Jonas Mielke , Guido Burkard , Jason R. Petta

The ferromagnetic state of an Ising chain can represent a two-fold degenerate subspace or equivalently a logical qubit which is protected from excitations by an energy gap. We study a a braiding-like exchange operation through the movement…

Quantum Physics · Physics 2021-08-11 Bassel Heiba Elfeky , Matthieu C. Dartiailh , S. M. Farzaneh , Javad Shabani

We provide the necessary framework for carrying out stochastic positive-P and gauge-P simulations of bosonic systems with long range interactions. In these approaches, the quantum evolution is sampled by trajectories in phase space,…

Quantum Physics · Physics 2017-07-19 S. Wüster , J. F. Corney , J. M. Rost , P. Deuar

Quantum many-body scars (QMBS) are exceptional energy eigenstates of quantum many-body systems associated with violations of thermalization for special non-equilibrium initial states. Their various systematic constructions require…

Strongly Correlated Electrons · Physics 2025-02-20 Alessio Lerose , Tommaso Parolini , Rosario Fazio , Dmitry A. Abanin , Silvia Pappalardi

Various quantum applications can be reduced to estimating expectation values, which are inevitably deviated by operational and environmental errors. Although errors can be tackled by quantum error correction, the overheads are far from…

Quantum Physics · Physics 2020-02-19 Shuaining Zhang , Yao Lu , Kuan Zhang , Wentao Chen , Ying Li , Jing-Ning Zhang , Kihwan Kim

Measurement-based quantum computing (MBQC) in linear optical systems is promising for near-future quantum computing architecture. However, the nondeterministic nature of entangling operations and photon losses hinder the large-scale…

Quantum Physics · Physics 2023-04-25 Seok-Hyung Lee , Srikrishna Omkar , Yong Siah Teo , Hyunseok Jeong

Semiconductor spin qubits demonstrated single-qubit gates with fidelities up to $99.9\%$ benchmarked in the single-qubit subspace. However, tomographic characterizations reveals non-negligible crosstalk errors in a larger space.…

Ion trap systems are a leading platform for large scale quantum computers. Trapped ion qubit crystals are fully-connected and reconfigurable, owing to their long range Coulomb interaction that can be modulated with external optical forces.…

We experimentally demonstrate a weak measurement and measurement reversal-based scheme to ameliorate the effects of decoherence due to amplitude damping, on an NMR quantum processor. The weak measurement and measurement reversal processes…

Quantum Physics · Physics 2024-09-20 Gayatri Singh , Akshay Gaikwad , Arvind , Kavita Dorai

In the noisy intermediate-scale quantum (NISQ) era, flexible quantum operations are essential for advancing large-scale quantum computing, as they enable shorter circuits that mitigate decoherence and reduce gate errors. However, the…

Quantum states featuring extensive multipartite entanglement are a resource for quantum-enhanced metrology, with sensitivity up to the Heisenberg limit. However, robust generation of these states using unitary dynamics typically requires…