Robust spin squeezing from the tower of states of U(1)-symmetric spin Hamiltonians

Comparin, Tommaso; Mezzacapo, Fabio; Roscilde, Tommaso

doi:10.1103/physreva.105.022625

Cited by 38 publications

(33 citation statements)

References 47 publications

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“…Recent works [12][13][14][15][16][17] have pointed out the robustness of spin-squeezing dynamics in models that deviate from one-axis-twisting Hamiltonians, and that strong squeezing can be found at Ising quantum critical points [18]. Our theorems include and generalize the Hamiltonians considered in these works.…”

Section: Introductionmentioning

confidence: 75%

Spin squeezing from bilinear spin-spin interactions: two simple theorems

Roscilde,

Mezzacapo,

Comparin

2021

Preprint

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We demonstrate two simple theorems about squeezing induced by bilinear spin-spin interactions that conserve spin parity -including a vast majority of quantum spin models implemented by state-of-the-art quantum simulators. In particular we show that squeezing captures the first form of quantum correlations which are produced: 1) at equilibrium, by adiabatically turning on the spin-spin interactions starting from a factorized state aligned with an external, arbitrary field; 2) away from equilibrium, by evolving unitarily the same state with the interacting Hamiltonian.

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Section: Introductionmentioning

confidence: 75%

Spin squeezing from bilinear spin-spin interactions: two simple theorems

Roscilde,

Mezzacapo,

Comparin

2021

Preprint

Self Cite

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“…Although, the ground state of the system reveals squeezing, its value can be enhanced through quench dynamics [86]. In this case, we initialize the system in the state |Ψ(0) = |0, 0, • • • , 0 .…”

Section: Spin Squeezingmentioning

confidence: 99%

Variational quantum simulation of long-range interacting systems

Tang¹,

Lyu²,

Li³

et al. 2022

Preprint

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Current quantum simulators suffer from multiple limitations such as short coherence time, noisy operations, faulty readout and restricted qubit connectivity. Variational quantum algorithms are the most promising approach in near-term quantum simulation to achieve quantum advantage over classical computers. Here, we explore variational quantum algorithms, with different levels of qubit connectivity, for digital simulation of the ground state of long-range interacting systems. We find that as the interaction becomes more long-ranged, the variational algorithms become less efficient, achieving lower fidelity and demanding more optimization iterations. In particular, when the system is near its criticality the efficiency is even lower. Increasing the connectivity between distant qubits improves the results, even with less quantum and classical resources. Our results show that by mixing circuit layers with different levels of connectivity one can sensibly improve the results. Interestingly, the order of layers becomes very important and grouping the layers with long-distance connectivity at the beginning of the circuit outperforms other permutations. The same design of circuits can also be used to variationally produce spin squeezed states, as a resource for quantum metrology. The quantum variational method indeed outperforms the ground state and quench dynamics approach for creating spin squeezing.

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“…In such systems, entanglement can be famously revealed by so-called spinsqueezing inequalities (SSI), which involve measurements of first-and second-moments of collective spin operators [26,32,35]. SSI and their generalizations [32,35] have found an impressively broad range of successful applications, from detecting entanglement in cold and hot atomic ensembles [19,26] to unveiling many-body Bell non-locality [6,25,27,30], from probing quantum phase transitions [9] and quantum quenches [4] to applications in quantum-enhanced metrology [26]. In particular, a handful of generalized SSI is sufficient to capture the complete palette of entanglement that can be revealed via collectivespin measurement in j = 1/2 spin ensembles [32].…”

Section: Introductionmentioning

confidence: 99%

Probing quantum entanglement from magnetic-sublevels populations: beyond spin squeezing inequalities

Müller-Rigat,

Lewenstein,

Frérot

2022

Preprint

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Spin squeezing inequalities (SSI) represent a major tool to probe quantum entanglement among a collection of few-level atoms, and are based on collective spin measurements and their fluctuations. Yet, for atomic ensembles of spin-j atoms and ultracold spinor gases, many experiments can image the populations in all Zeeman sublevels s = −j, −j + 1, . . . , j, potentially revealing finer features of quantum entanglement not captured by SSI. Here we present a systematic approach which exploits Zeeman-sublevel population measurements in order to construct novel entanglement criteria, and illustrate our approach on ground states of spin-1 and spin-2 Bose-Einstein condensates. Beyond these specific examples, our approach allows one to infer, in a systematic manner, the optimal permutationally-invariant entanglement witness for any given set of collective measurements in an ensemble of dlevel quantum systems.

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Robust spin squeezing from the tower of states of U(1)-symmetric spin Hamiltonians

Cited by 38 publications

References 47 publications

Spin squeezing from bilinear spin-spin interactions: two simple theorems

Spin squeezing from bilinear spin-spin interactions: two simple theorems

Variational quantum simulation of long-range interacting systems

Probing quantum entanglement from magnetic-sublevels populations: beyond spin squeezing inequalities

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