Qudits for witnessing quantum-gravity-induced entanglement of masses under decoherence

Tilly, Jules; Marshman, Ryan J.; Mazumdar, Anupam; Bose, Sougato

doi:10.1103/physreva.104.052416

Cited by 41 publications

(39 citation statements)

References 46 publications

(73 reference statements)

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“…[74] or "parallel" in Ref. [75]. By increasing the depth of the magnets in the y direction, and dropping two diamonds offset in y, two identical superpositions could be generated simultaneously.…”

Section: Discussionmentioning

confidence: 99%

Spin dynamical decoupling for generating macroscopic superpositions of a free-falling nanodiamond

2022

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Levitated nanodiamonds containing negatively charged nitrogen-vacancy centers (NV − ) have been proposed as a platform to generate macroscopic spatial superpositions. Requirements for this include having a long NV − spin coherence time, which necessitates formulating a dynamical decoupling strategy in which the regular spin flips do not cancel the growth of the superposition through the Stern-Gerlach effect in an inhomogeneous magnetic field. Here, we propose a scheme to place a 250-nm-diameter diamond in a superposition with spatial separation of over 250 nm, while incorporating dynamical decoupling. We achieve this by letting a diamond fall for 2.4 m through a magnetic structure, including 1.13 m in an inhomogeneous region generated by magnetic teeth.

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Section: Discussionmentioning

confidence: 99%

Spin dynamical decoupling for generating macroscopic superpositions of a free-falling nanodiamond

2022

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“…Many possible improvements to the original setup have already been discussed, using a different witness [19], ways of creating macroscopic quantum superposition [16], including effects due to decoherence [19,40], ameliorating Casimirinduced entanglement [17], taming gravity gradient noise and relative acceleration [18,20], a different configuration of the superpositions [14], using higher-dimensional quantum objects [24], or using different measurement bases [41]. Furthermore, Refs.…”

Section: Introductionmentioning

confidence: 99%

Improving resilience of quantum-gravity-induced entanglement of masses to decoherence using three superpositions

et al. 2022

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Recently, a protocol called quantum-gravity-induced entanglement of masses (QGEM) that aims to test the quantum nature of gravity using the entanglement of two qubits was proposed. The entanglement can arise only if the force between the two spatially superposed masses is occurring via the exchange of a mediating virtual graviton. In this paper we examine a possible improvement of the QGEM setup by introducing a third mass with an embedded qubit so that there are now three qubits to witness the gravitationally generated entanglement. We compare the entanglement generation for different experimental setups with two and three qubits and find that a three-qubit setup where the superpositions are parallel to each other leads to the highest rate of entanglement generation within τ = 5 s. We show that the three-qubit setup is more resilient to the higher rate of decoherence. The entanglement can be detected experimentally for the two-qubit setup if the decoherence rate γ is γ < 0.11 Hz compared to γ < 0.16 Hz for the three-qubit setup. However, the introduction of an extra qubit means that more measurements are required to characterize entanglement in an experiment. We conduct experimental simulations and estimate that the three-qubit setup would allow detecting the entanglement in the QGEM protocol at a 99.9% certainty with O(10 4 )-O(10 5 ) measurements when γ ∈ [0.1, 0.15] Hz. Furthermore, we find that the number of needed measurements can be reduced to O(10 3 )-O(10 5 ) if the measurement schedule is optimized using joint Pauli basis measurements. For γ > 0.06 Hz the three-qubit setup is favorable compared to the two-qubit setup in terms of the minimum number of measurements needed to characterize the entanglement. Thus, the proposed setup here provides a promising avenue for implementing the QGEM experiment.

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“…The entanglement due to gravity has been becoming a benchmark for the quantum nature of gravity [1,2]. In sympathy with its importance, there were several theoretical works on various experimental proposals, for example, matter-wave interferometers [3][4][5][6][7], mechanical oscillators [8,9], optomechanical systems [10][11][12][13], and those hybrid systems [14][15][16].…”

Section: Conclusion 21 I Introductionmentioning

confidence: 99%

Role of matter coherence in entanglement due to gravity

Matsumura¹

2022

Preprint

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We investigate the quantum nature of gravitational interaction in terms of the coherence of quantum objects. As a basic setting, we consider two gravitating objects each in a superposition state of two paths. The evolution of objects is described by the completely positive and tracepreserving (CPTP) map with a population-preserving property. This property reflects that the probability of objects being on each path is preserved. We use the 1 -norm of coherence to quantify the coherence of objects. The quantum nature of gravitational interaction is characterized by an entangling map, which is a CPTP map with the capacity to create entanglement. We introduce the entangling-map witness as an observable to test whether a given map is entangling. We show that, whenever the gravitating objects initially have a finite amount of the 1 -norm of coherence, the witness tests the entangling map due to gravity. Interestingly, we find that the witness can capture the signature of the entangling map due to gravity, even when the objects do not get entangled. This means that the coherence of gravitating objects always becomes the source of the entangling map due to gravity. We further discuss a decoherence effect and an experimental perspective in the present approach.

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Qudits for witnessing quantum-gravity-induced entanglement of masses under decoherence

Cited by 41 publications

References 46 publications

Spin dynamical decoupling for generating macroscopic superpositions of a free-falling nanodiamond

Spin dynamical decoupling for generating macroscopic superpositions of a free-falling nanodiamond

Improving resilience of quantum-gravity-induced entanglement of masses to decoherence using three superpositions

Role of matter coherence in entanglement due to gravity

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