Estimating Coherence Measures from Limited Experimental Data Available

Zhang, Da-Jian; Liu, C. L.; Yu, Xiao-Dong; Tong, D. M.

doi:10.1103/physrevlett.120.170501

Cited by 44 publications

(24 citation statements)

References 53 publications

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“…We note that while the interference visibility V has traditionally been considered as a signature of coherence, there have been cases whereunder certain conditionsan enhancement of V was observed with increasing decoherence 33,34 , thus creating doubt on its efficacy as a true signature. Furthermore, newer measures of coherence, for example, based on the l 1 -norm of the offdiagonal elements of the density matrix of the quanton, has been developed [35][36][37] which replaced V in the generalized duality relations to capture the correct variation of coherence with decoherence 38 . However, scattering from a 'smooth' regular surface ensures that the number of possible interference paths is restricted to two for which the l 1 -norm based coherence is identical to the interference visibility V 38,39 .…”

Section: Results Experimentsmentioning

confidence: 99%

Observing quantum coherence from photons scattered in free-space

Sajeed

Jennewein

2021

Light Sci Appl

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Quantum channels in free-space, an essential prerequisite for fundamental tests of quantum mechanics and quantum technologies in open space, have so far been based on direct line-of-sight because the predominant approaches for photon-encoding, including polarization and spatial modes, are not compatible with randomly scattered photons. Here we demonstrate a novel approach to transfer and recover quantum coherence from scattered, non-line-of-sight photons analyzed in a multimode and imaging interferometer for time-bins, combined with photon detection based on a 8 × 8 single-photon-detector-array. The observed time-bin visibility for scattered photons remained at a high 95% over a wide scattering angle range of −450 to +450, while the individual pixels in the detector array resolve or track an image in its field of view of ca. 0.5°. Using our method, we demonstrate the viability of two novel applications. Firstly, using scattered photons as an indirect channel for quantum communication thereby enabling non-line-of-sight quantum communication with background suppression, and secondly, using the combined arrival time and quantum coherence to enhance the contrast of low-light imaging and laser ranging under high background light. We believe our method will instigate new lines for research and development on applying photon coherence from scattered signals to quantum sensing, imaging, and communication in free-space environments.

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Section: Results Experimentsmentioning

confidence: 99%

Observing quantum coherence from photons scattered in free-space

Sajeed

Jennewein

2021

Light Sci Appl

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“…Recently, quantum coherence is a resurgent concept in the quantum theory and acts as a manifestation of the quantum superposition principle. We also recall the l 1 norm of coherence [58], which can almost be estimated in experiments [59,60]. For a density matrix ρ in the reference basis {|i }, l 1 norm of coherence is given by…”

Section: Resultsmentioning

confidence: 99%

Phase Diagram of the Spin-1/2 Heisenberg Alternating Chain in a Magnetic Field*

Chen¹,

Ren²,

You³

et al. 2019

Commun. Theor. Phys.

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By using the infinite time-evolving block decimation, we study quantum fidelity and entanglement entropy in the spin-1/2 Heisenberg alternating chain under an external magnetic field. The effects of the magnetic field on the fidelity are investigated, and its relation with the quantum phase transition (QPT) is analyzed. The phase diagram of the model is given accordingly, which supports the Haldane phase, the singlet-dimer phase, the Luttinger liquid phase and the paramagnetic phase. The scaling of entanglement entropy in the gapless Luttinger liquid phase is studied, and the central charge c = 1 is obtained. We also study the relationship between the quantum coherence, string order parameter and QPTs. Results obtained from these quantum information observations are consistent with the previous reports.

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“…where c † µ,k is the fermionic creation operator at quasimomentum k for the sublattice site indexed by µ in each unit cell. It is worth noting that the l 1 norm of coherence can be estimated in experiments by other means 47 . Here, we shall connect this coherence measure with charge pumping which is also experimentally accessible in a rather direct way.…”

Section: Entanglement Entropy and Coherence Measurementioning

confidence: 99%

Revealing many-body effects on interband coherence through adiabatic charge pumping

Zhang

Zhou

et al. 2019

Phys. Rev. B

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The adiabatic charge pumping of a non-equilibrium state of spinless fermions in a one-dimensional lattice is investigated, with an emphasis placed on its usefulness in revealing many-body interaction effects on interband coherence. For a non-interacting system, the pumped charge per adiabatic cycle depends not only on the topology of the occupied bands but also on the interband coherence in the initial state. This insight leads to an interesting opportunity for quantitatively observing how quantum coherence is affected by many-body interaction that is switched on for a varying duration prior to adiabatic pumping. In particular, interband coherence effects can be clearly observed by adjusting the switch-on rates with different adiabatic pumping protocols and by scanning the duration of many-body interaction prior to adiabatic pumping. The time dependence of singleparticle interband coherence in the presence of many-body interaction can then be examined in detail. As a side but interesting result, for relatively weak interaction strength, it is found that the difference in the pumped charges between different pumping protocols vanishes if a coherence measure defined from the single-particle density matrix in the sublattice representation reaches its local minima. Our results hence provide an interesting means to quantitatively probe the dynamics of quantum coherence in the presence of many-body interaction (e.g., in a thermalization process).

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Estimating Coherence Measures from Limited Experimental Data Available

Cited by 44 publications

References 53 publications

Observing quantum coherence from photons scattered in free-space

Observing quantum coherence from photons scattered in free-space

Phase Diagram of the Spin-1/2 Heisenberg Alternating Chain in a Magnetic Field*

Revealing many-body effects on interband coherence through adiabatic charge pumping

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