Quantum Polarization Spectroscopy of Ultracold Spinor Gases

Eckert, K.; Zawitkowski, L.; Sanpera, Anna; Lewenstein, Maciej; Polzik, E. S.

doi:10.1103/physrevlett.98.100404

Cited by 48 publications

(68 citation statements)

References 26 publications

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“…Furthermore, the state of such effective spin models can be probed by resorting to a nondemolition scheme based on quantum polarization spectroscopy [53]: The angular momentum of the sample may be coupled to the polarization of an incident laser beam and read out by homodyne detection of the scattered light [54][55][56].…”

Section: A the One-dimensional X X Modelmentioning

confidence: 99%

Achieving sub-shot-noise sensing at finite temperatures

2016

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We investigate sensing of magnetic fields using quantum spin chains at finite temperature and exploit quantum phase crossovers to improve metrological bounds on the estimation of the chain parameters. In particular, we start by analyzing the XX spin chain. The magnetic sensitivity of this system is dictated by its magnetic susceptibility, which scales extensively (linearly) in the number of spins N . We introduce an iterative feed-forward protocol that actively exploits features of quantum phase crossovers to enable superextensive scaling of the magnetic sensitivity. Furthermore, we provide experimentally realistic observables to saturate the quantum metrological bounds. Finally, we extend our analysis on magnetic sensing to the Heisenberg XY spin chain.

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Section: A the One-dimensional X X Modelmentioning

confidence: 99%

Achieving sub-shot-noise sensing at finite temperatures

2016

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“…The antiferromagnetic Néel state appearing in the 2D Heisenberg model can be indeed detected with the method of Ref. [17]. Fermionic superfluidity Another application of our scheme is to detect superfluid phases in fermionic ultracold gases in a QND way.…”

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confidence: 99%

“…In particular, atomic squeezing [15], atomic entanglement, quantum memory, and teleportation have been achieved in this context (for a review see [16] and references therein). We have recently proposed to apply this approach to detect magnetic order of weakly correlated ultracold atoms [17]. Unfortunately, such proposal does not provide spatial resolution, and thus it cannot, e.g., discriminate between different antiferromagnetic quantum phases present in lattice models.…”

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confidence: 99%

Quantum non-demolition detection of strongly correlated systems

et al. 2007

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Preparation, manipulation, and detection of strongly correlated states of quantum many body systems are among the most important goals and challenges of modern physics. Ultracold atoms offer an unprecedented playground for realization of these goals. Here we show how strongly correlated states of ultracold atoms can be detected in a quantum non-demolition scheme, that is, in the fundamentally least destructive way permitted by quantum mechanics. In our method, spatially resolved components of atomic spins couple to quantum polarization degrees of freedom of light. In this way quantum correlations of matter are faithfully mapped on those of light; the latter can then be efficiently measured using homodyne detection. We illustrate the power of such spatially resolved quantum noise limited polarization measurement by applying it to detect various standard and "exotic" types of antiferromagnetic order in lattice systems and by indicating the feasibility of detection of superfluid order in Fermi liquids.Introduction Future applications of quantum physics for quantum simulations, computation, communication, and metrology will require an extremely high degree of control of preparation, manipulation, and, last but not least, detection of strongly correlated states of quantum many body systems. Ultracold atoms offer an unprecedented playground for realization of these goals. Several paradigm examples of strongly correlated states have been successfully realized, such as the Mott insulator, the Tonks gas, and the Bose glass (for a review cf. [1]). A standard way of analyzing such systems is by releasing the atoms from the trap and performing destructive absorption spectroscopy, which only allows to measure the column density of the expanded cloud. Considerable attention has been thus devoted recently to novel methods of detection, that allow for measuring (spin) densitydensity and other higher order correlation functions. One of those methods is atomic noise interferometry [2], whose power is well illustrated in the recent observation of the bosonic and the fermionic Hanbury Brown-Twiss effect [3,4]. Direct atom counting is another way to measure this effect, and to even go beyond it [5]; it can be realized directly with metastable Helium atoms [6,7], or by using methods of cavity quantum electrodynamics (QED) [8]. Cavity QED is also essential in the recent proposals of Ref. [9,10], while Ref. [11] proposes how to prepare and detect magnetic quantum phases using superlattices. All of the above approaches are, at least in some respects, destructive and frequently suffer from undesired atom number fluctuations inevitable in the preparation of the quantum states.

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“…The original proposal by Braginsky [1] in the context of gravitational wave detection has been generalized to the optical [2, 3], atomic [4] and nano-mechanical [5] domains. In the atomic domain, QND by dispersive optical probing of spins or pseudospins has been demonstrated using ensembles of cold atoms on a clock transition [6,7], and with polarization variables [8,9], but thus far only with real or effective spin-1/2 systems.QND measurement of larger spin systems offers a metrological advantage, e.g., in magnetometry [10], and may be essential for the detection of different quantum phases of degenerate atomic gases that intrinsically rely on large-spin systems [11][12][13]. Dispersive interactions with large-spin atoms are complicated by the presence of non-QND-type terms in the effective Hamiltonian describing the interaction [14-16].…”

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Quantum Nondemolition Measurement of Large-Spin Ensembles by Dynamical Decoupling

et al. 2010

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Quantum non-demolition (QND) measurement of collective variables by off-resonant optical probing has the ability to create entanglement and squeezing in atomic ensembles. Until now, this technique has been applied to real or effective spin one-half systems. We show theoretically that the build-up of Raman coherence prevents the naive application of this technique to larger spin atoms, but that dynamical decoupling can be used to recover the ideal QND behavior. We experimentally demonstrate dynamical decoupling by using a two-polarization probing technique. The decoupled QND measurement achieves a sensitivity 5.7(6) dB better than the spin projection noise.PACS numbers: 42.50. Lc, 07.55.Ge, 42.50.Dv, 03.67.Bg Quantum non-demolition measurement plays a central role in quantum networking and quantum metrology for its ability to simultaneously detect and generate non-classical quantum states. The original proposal by Braginsky [1] in the context of gravitational wave detection has been generalized to the optical [2, 3], atomic [4] and nano-mechanical [5] domains. In the atomic domain, QND by dispersive optical probing of spins or pseudospins has been demonstrated using ensembles of cold atoms on a clock transition [6,7], and with polarization variables [8,9], but thus far only with real or effective spin-1/2 systems.QND measurement of larger spin systems offers a metrological advantage, e.g., in magnetometry [10], and may be essential for the detection of different quantum phases of degenerate atomic gases that intrinsically rely on large-spin systems [11][12][13]. Dispersive interactions with large-spin atoms are complicated by the presence of non-QND-type terms in the effective Hamiltonian describing the interaction [14-16]. As we show, and contrary to what has often been assumed [11][12][13]17], these terms spoil the QND performance, even in the largedetuning limit. The non-QND terms introduce noise into the measured variable, or equivalently decoherence into the atomic state. The problem is serious for both large and small ensembles, so that naive application of dispersive probing fails for several of the above-cited proposals.We approach this problem using the methods of dynamical decoupling [18][19][20], which allow us to effectively cancel the non-QND terms in the Hamiltonian while retaining the QND term. To our knowledge, this is the first application of this method to quantum non-demolition measurements. Dynamical decoupling has been extensively applied in magnetic resonance [21,22], used to suppress collisional decoherence in a thermal vapor [23], to extend coherence times in solids [24], in Rydberg atoms [25], and with photon polarization [26]. Other approaches include application of a static perturbation [27,28].We consider an ensemble of spin-f atoms interacting with a pulse of near-resonant polarized light. As described in references [14][15][16], the light and atoms interact by the effective HamiltonianĤ effwhere τ is the duration of the pulse and G 1,2 are coupling constants that depend on the ato...

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Quantum Polarization Spectroscopy of Ultracold Spinor Gases

Cited by 48 publications

References 26 publications

Achieving sub-shot-noise sensing at finite temperatures

Achieving sub-shot-noise sensing at finite temperatures

Quantum non-demolition detection of strongly correlated systems

Quantum Nondemolition Measurement of Large-Spin Ensembles by Dynamical Decoupling

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