Mesoscopic quantum superpositions in bimodal Bose-Einstein condensates: Decoherence and strategies to counteract it

Pawłowski, Krzysztof; Fadel, Matteo; Treutlein, Philipp; Castin, Yvan; Sinatra, Alice

doi:10.1103/physreva.95.063609

Cited by 35 publications

(28 citation statements)

References 48 publications

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“…It is one of the challenging tasks to create truly macroscopic cat states in atomic systems. Bosonic Josephson junctions, which consist of two coupled Bose-Einstein condensates via Josephson coupling, have been investigated to generate macroscopic cat states [47][48][49][50][51][52][53][54][55][56][57][58][59]. Note that if there is no energy imbalance between two modes of Bose-Einstein condensates, bosonic Josephson junctions are equivalent to the Lipkin-Meshkov-Glick model in the collective spin expression [60][61][62].…”

Section: Introductionmentioning

confidence: 99%

Shortcuts to adiabatic cat-state generation in bosonic Josephson junctions

Hatomura¹

2018

New J. Phys.

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We propose a quantum speedup method for adiabatic generation of cat states in bosonic Josephson junctions via shortcuts to adiabaticity. We apply approximated counter-diabatic driving to a bosonic Josephson junction using the Holstein-Primakoff transformation. In order to avoid the problem of divergence in counter-diabatic driving, we take finite-size corrections into account. The resulting counter-diabatic driving is well-defined over whole processes. Schedules of the counter-diabatic driving consist of three steps; the counter-diabatic driving in the disordered phase, smoothly and slowly approaching the critical point, and the counter-diabatic driving in the ordered phase. Using the counter-diabatic driving, adiabatic generation of cat states is successfully accelerated. The enough large quantum Fisher information ensures that generated cat states are highly entangled. difficulty to find shortcuts depends on the sign of the nonlinear interaction. The ground state of the antiferromagnetic Lipkin-Meshkov-Glick model is the spin-squeezed Dicke state, which is unique and has been successfully produced using shortcuts to adiabaticity with high fidelity and within short time [77,79,81]. In contrast, the ground state of the ferromagnetic Lipkin-Meshkov-Glick model is the cat state. Shortcuts to adiabaticity in the ferromagnetic Lipkin-Meshkov-Glick model was first studied by Takahashi using the Holstein-Primakoff transformation in the thermodynamic limit [78]. Counter-diabatic driving was derived for both the disordered and the ordered phases. However, this counter-diabatic driving is ill-defined, i.e., diverges, at the critical point unless the fixed-point condition is satisfied. As discussed in literatures, especially in [80], this divergence is associated with the closing of the gap and the divergence of the correlation length. Campbell et al studied counter-diabatic driving around the critical point applying various approaches, especially in combination with optimal control [80]. By applying a small longitudinal field, which enables us to slightly avoid the critical point, mean-field prescription was applied both in the invariant-based inverse engineering approach [82] and the counter-diabatic driving approach [83].In this paper, we propose approximated counter-diabatic driving for bosonic Josephson junctions without energy imbalance, which is available across the critical point, using finite-size corrections in the Holstein-Primakoff transformation. Advantages of our method are that the counter-diabatic driving is well-defined over whole processes and that schedules of the counter-diabatic driving can be analytically obtained. Using our counter-diabatic driving, we can accelerate adiabatic generation of the cat state. Schedules of the counterdiabatic driving consist of three steps. The first one is the counter-diabatic driving in the disordered phase, where we aim to let the system be in the ground state. The second one is smoothly and slowly approaching the critical point, where we give up to be adiabatic but ai...

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Section: Introductionmentioning

confidence: 99%

Shortcuts to adiabatic cat-state generation in bosonic Josephson junctions

Hatomura¹

2018

New J. Phys.

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“…If a spontaneous emission event occurs, we will call the event "distinguishable" if, in principle, it is possible to determine which component of the SC state produced the photon; otherwise, we will call the event "indistinguishable." If the emission is distinguishable, then the SC state would collapse to a single collective state, and there would be no interference [53,54]. The distinguishablity of the emission event will be determined by the size of D. The relevant length scale here is the wavelength of the emitted photon: λ P .…”

Section: B One Axis Twist Squeezing: Effect Of Non-idealitiesmentioning

confidence: 99%

“…As discussed, for example, in Refs. [54] and [53], this can be of potentially significant concern in creating SC states of Bose-condensed atoms. However, for the systems being considered here, the density of atoms is small enough to ignore collisions among the atoms in the SC state.…”

Section: B One Axis Twist Squeezing: Effect Of Non-idealitiesmentioning

confidence: 99%

Increasing Sensitivity of an Atom Interferometer to the Heisenberg Limit using Enhanced Quantum Noise

Fang¹,

Sarkar²,

Shahriar³

2018

Frontiers in Optics / Laser Science

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In a conventional atomic interferometer employing N atoms, the phase sensitivity is at the standard quantum limit: 1/ √ N . Using spin-squeezing, the sensitivity can be increased, either by lowering the quantum noise or via phase amplification, or a combination thereof. Here, we show how to increase the sensitivity, to the Heisenberg limit of 1/N , while increasing the quantum noise by √ N , thereby suppressing by the same factor the effect of excess noise. The proposed protocol makes use of a Schrödinger Cat state representing a mesoscopic superposition of two collective states of N atoms, behaving as a single entity with an N -fold increase in Compton frequency. The resulting N -fold phase magnification is revealed by using atomic state detection instead of collective state detection. We also show how to realize an atomic clock based on such a Schrödinger Cat state, with an N -fold increase in the effective transition frequency. We also discuss potential experimental constraints for implementing this scheme, using one axis twist squeezing employing the cavity feedback scheme, and show that the effects of cavity decay and spontaneous emission are highly suppressed due to the N -fold phase magnification. We find that even for a modest value of the cavity cooperativity parameter that should be readily accessible experimentally, the maximum improvement in sensitivity is very close to the ideal limit, for as many as ten million atoms.PACS numbers: 06.30. Gv, 03.75.Dg, 37.25.+k Using the fact that Ȯ = tr(ρÔ) for any operatorÔ, it

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“…The presence of interactions among the atoms in a matter-wave interferometer leads to several relevant effects that have been investigated in the literature [2,[29][30][31][32][33][34][35][36]. In particular, these include the connection between the Heisenberg limit, in which sub-shot noise can be achieved, and multiparticle entanglement useful for metrology, measured by the Fisher information [1,4,32,37].…”

Section: Introductionmentioning

confidence: 99%

Effect of Inter-Well Interactions on Non-Linear Beam Splitters for Matter-Wave Interferometers

et al. 2020

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We study the non-linear beam splitter in matter-wave interferometers using ultracold quantum gases in a double-well configuration in presence of non-local interactions inducing inter-well density-density coupling, as they can be realized, e.g., with dipolar gases. We explore this effect after considering different input states, in the form of either coherent, or Twin-Fock, or NOON states. We first review the non-interacting limit and the case in which only the local interaction is present, including the study of sensitivity near the self-trapping threshold. Then, we consider the two-mode model in the presence of inter-well interactions and consider the scaling of the sensitivity as a function of the non-local coupling strength. Our analysis clearly shows that non-local interactions can compensate the degradation of the sensitivity induced by local interactions, so that they may be used to restore optimal sensitivity.

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Mesoscopic quantum superpositions in bimodal Bose-Einstein condensates: Decoherence and strategies to counteract it

Cited by 35 publications

References 48 publications

Shortcuts to adiabatic cat-state generation in bosonic Josephson junctions

Shortcuts to adiabatic cat-state generation in bosonic Josephson junctions

Increasing Sensitivity of an Atom Interferometer to the Heisenberg Limit using Enhanced Quantum Noise

Effect of Inter-Well Interactions on Non-Linear Beam Splitters for Matter-Wave Interferometers

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