Planar squeezing by quantum non-demolition measurement in cold atomic ensembles

Puentes, Graciana; Colangelo, Giorgio; Sewell, R. J.; Mitchell, Morgan W.

doi:10.1088/1367-2630/15/10/103031

Cited by 35 publications

(50 citation statements)

References 40 publications

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“…Modematching and spatial effects are important for other spin squeezing protocols including the double-pass countertwisting interaction [51,52] or the recently proposed planar squeezing protocol [53]. Understanding spatial effects in order to identify regimes of strong coupling is also essential for quantum memories and repeaters in free-space atomic ensembles.…”

Section: Discussionmentioning

confidence: 99%

Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles

et al. 2014

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We study the three-dimensional nature of the quantum interface between an ensemble of cold, trapped atomic spins and a paraxial laser beam, coupled through a dispersive interaction. To achieve strong entanglement between the collective atomic spin and the photons, one must match the spatial mode of the collective radiation of the ensemble with the mode of the laser beam while minimizing the effects of decoherence due to optical pumping. For ensembles coupling to a probe field that varies over the extent of the cloud, the set of atoms that indistinguishably radiates into a desired mode of the field defines an inhomogeneous spin wave. Strong coupling of a spin wave to the probe mode is not characterized by a single parameter, the optical density, but by a collection of different effective atom numbers that characterize the coherence and decoherence of the system. To model the dynamics of the system, we develop a full stochastic master equation, including coherent collective scattering into paraxial modes, decoherence by local inhomogeneous diffuse scattering, and backaction due to continuous measurement of the light entangled with the spin waves. This formalism is used to study the squeezing of a spin wave via continuous quantum nondemolition (QND) measurement. We find that the greatest squeezing occurs in parameter regimes where spatial inhomogeneities are significant, far from the limit in which the interface is well approximated by a one-dimensional, homogeneous model.

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Section: Discussionmentioning

confidence: 99%

Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles

et al. 2014

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“…Given that most atomic ensemble experiments are performed with spin-1 or larger atoms, the technique described here will allow more accurate modelling of established quantum optical protocols, e.g. quantum memory [15], quantum non-demolition measurement [26,38], dynamical decoupling [25], spin squeezing [8] and vector magnetometry [36], as well as proposed applications such as generation of macroscopic singlet states [42,43] and planar squeezed states [37].…”

Section: Discussionmentioning

confidence: 99%

“…The transverse relaxation time T = 1/(wγ |B |) is due to the field-parallel gradient component B ≡ ∂|B|/∂ z , and a Lorentzian distribution (FWHM w) of atoms along z, the trap axis, as described in appendix C. Tensorial light shifts induce an additional nonlinear rotation of the atomic spins, as described in Smith et al [20] and Deutsch and Jessen [31]. This measurement can be used to estimate an unknown vector magnetic field, as in Behbood et al [36], and is the basis of a proposal to prepare a planar-squeezed atomic spin state [37]. Our experimental apparatus, illustrated in figure 2, has been described in detail elsewhere [8,25,38,39].…”

Section: An Example: Free-induction Decay Of Collective Atomic Spinmentioning

confidence: 99%

Quantum atom–light interfaces in the Gaussian description for spin-1 systems

et al. 2013

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We extend the covariance matrix description of atom-light quantum interfaces, originally developed for real and effective spin-1/2 atoms, to include 'spin alignment' degrees of freedom. This allows accurate modelling of optically probed spin-1 ensembles in arbitrary magnetic fields. We also include technical noise terms that are very common in experimental situations. These include magnetic field noise, variable atom number and the effect of magnetic field inhomogeneities. We demonstrate the validity of our extended model by comparing numerical simulations to a free-induction decay measurement of polarized 87 Rb atoms in the f = 1 ground state. We qualitatively and quantitatively reproduce experimental results with no free parameters. The model can be easily extended to larger spin systems, and adapted to more complicated experimental situations. 4 These authors contributed equally to this work.

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“…The result show that ∀j ε gs,X (j) ≤ V min1 XZ (j) ≤ V min2 XZ (j) and the ground state energy of H T ot,X provide a fairly good and meaningful lower bound. (11); ( yellow triangles) V min 2 XZ (j) as in (12). Right: Relative errors obtained with the use of |θm = exp (−iθmHT AS ) |j, j (see text) as a function of j = 1, .., 100.…”

Section: B Spin Operators and Planar Squeezingmentioning

confidence: 99%

State-independent uncertainty relations from eigenvalue minimization

2019

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We consider uncertainty relations that give lower bounds to the sum of variances. Finding such lower bounds is typically complicated, and efficient procedures are known only for a handful of cases. In this paper we present procedures based on finding the ground state of appropriate Hamiltonian operators, which can make use of the many known techniques developed to this aim. To demonstrate the simplicity of the method we analyze multiple instances, both previously known and novel, that involve two or more observables, both bounded and unbounded. arXiv:1810.09775v1 [quant-ph]

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Planar squeezing by quantum non-demolition measurement in cold atomic ensembles

Cited by 35 publications

References 40 publications

Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles

Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles

Quantum atom–light interfaces in the Gaussian description for spin-1 systems

State-independent uncertainty relations from eigenvalue minimization

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