A pedagogical introduction to continuously monitored quantum systems and measurement-based feedback

Albarelli, Francesco; Genoni, Marco G.

doi:10.1016/j.physleta.2023.129260

Cited by 4 publications

(4 citation statements)

References 53 publications

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“…The horizontal dashed line indicates the SQL. The (purple) dot-dashed line is the analytical scaling ξ 2 NF,m (27), while the (blue) dotted line is the analytical Heisenberg scaling in presence of feedback ξ 2 F,m (12).…”

Section: Numerical Results For the Full Atom-field Dynamicsmentioning

confidence: 99%

“…The dynamics of the internal system is described by a stochastic master equation (SME) for the density matrix conditioned on the measurement outcome ρc , which contains a decoherence term, due to the interaction with the external environment, and a stochastic term which instead describes the non-linear evolution of the system due to the performed measurement [27,28]:…”

Section: Continuous Measurement Dynamicsmentioning

confidence: 99%

“…Measurement protocols based on continuous monitoring [27] have been extensively studied for quantum state engineering purposes [28,29], leading to the outstanding experimental results observed in [30][31][32] for the cooling of a quantum mechanical oscillator towards its quantum ground state. In particular much theoretical effort has been devoted to the exploitation of this kind of protocols for the generation of metrologically useful quantum states, such as squeezed states of quantum harmonic oscillators or of SSSs for atomic ensembles [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52].…”

Section: Introductionmentioning

confidence: 99%

“…The vertical dashed line indicates the boundary of the bad-cavity condition as defined by(8), and empty symbols are outside said regime. The dotted line reports the numerical cavity removal result, which, for N = 45, is more accurate than equation(27).…”

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confidence: 98%

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Analysis of spin-squeezing generation in cavity-coupled atomic ensembles with continuous measurements

Caprotti,

Barbiero,

Tarallo

et al. 2024

Quantum Sci. Technol.

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We analyze the generation of spin-squeezed states via coupling of three-level atoms to an optical cavity and continuous quantum measurement of the transmitted cavity field in order to monitor the evolution of the atomic ensemble. Using analytical treatment and microscopic simulations of the dynamics, we show that one can achieve significant spin squeezing, favorably scaling with the number of atoms $N$. However, contrary to some previous literature, we clarify that it is not possible to obtain Heisenberg scaling without the continuous feedback that is proposed in optimal approaches. In fact, in the adiabatic cavity removal approximation and large $N$ limit, we find the scaling behavior $N^{-2/3}$ for spin squeezing and $N^{-1/3}$ for the corresponding protocol duration. These results can be obtained only by considering the curvature of the Bloch sphere, since linearizing the collective spin operators tangentially to its equator yields inaccurate predictions.With full simulations, we characterize how spin-squeezing generation depends on the system parameters and departs from the bad cavity regime, by gradually mixing with cavity-filling dynamics until metrological advantage is lost. Finally, we discuss the relevance of this spin-squeezing protocol to state-of-the-art optical clocks.

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Section: Numerical Results For the Full Atom-field Dynamicsmentioning

confidence: 99%

Section: Continuous Measurement Dynamicsmentioning

confidence: 99%