| 1. |
- Cotler, Jordan, et al.
(författare)
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Entanglement Enabled Intensity Interferometry of different wavelengths of light
- 2021
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Ingår i: Annals of Physics. - : Elsevier BV. - 0003-4916 .- 1096-035X. ; 424
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Tidskriftsartikel (refereegranskat)abstract
- We propose methods to perform intensity interferometry of photons having two different wavelengths. Distinguishable particles typically cannot interfere with each other, but we overcome that obstacle by processing the particles via entanglement and projection so that they lead to the same final state at the detection apparatus. Specifically, we discuss how quasi-phase-matched nonlinear crystals can be used to convert a quantum superposition of light of different wavelengths onto a common wavelength, while preserving the phase information essential for their meaningful interference. We thereby gain access to a host of new observables, which can probe subtle frequency correlations and entanglement. Further, we generalize the van Cittert-Zernike formula for the intensity interferometry of extended sources, demonstrate how our proposal supports enhanced resolution of sources with different spectral character, and suggest potential applications.
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| 2. |
- Cotler, Jordan, et al.
(författare)
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Quantum Overlapping Tomography
- 2020
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 124:10
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Tidskriftsartikel (refereegranskat)abstract
- It is now experimentally possible to entangle thousands of qubits, and efficiently measure each qubit in parallel in a distinct basis. To fully characterize an unknown entangled state of n qubits, one requires an exponential number of measurements in n, which is experimentally unfeasible even for modest system sizes. By leveraging (i) that single-qubit measurements can be made in parallel, and (ii) the theory of perfect hash families, we show that all k-qubit reduced density matrices of an n qubit state can be determined with at most e(O(k)) log(2) (n) rounds of parallel measurements. We provide concrete measurement protocols which realize this bound. As an example, we argue that with near-term experiments, every two-point correlator in a system of 1024 qubits could be measured and completely characterized in a few days. This corresponds to determining nearly 4.5 million correlators.
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| 3. |
- Cotler, Jordan, et al.
(författare)
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Superdensity operators for spacetime quantum mechanics
- 2018
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :9
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Tidskriftsartikel (refereegranskat)abstract
- We introduce superdensity operators as a tool for analyzing quantum information in spacetime. Superdensity operators encode spacetime correlation functions in an operator framework, and support a natural generalization of Hilbert space techniques and Dirac's transformation theory as traditionally applied to standard density operators. Superdensity operators can be measured experimentally, but accessing their full content requires novel procedures. We demonstrate these statements on several examples. The superdensity formalism suggests useful definitions of spacetime entropies and spacetime quantum channels. For example, we show that the von Neumann entropy of a superdensity operator is related to a quantum generalization of the Kolmogorov-Sinai entropy, and compute this for a many-body system. We also suggest experimental protocols for measuring spacetime entropies.
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| 4. |
- Liu, Lu-Chuan, et al.
(författare)
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Improved Spatial Resolution Achieved by Chromatic Intensity Interferometry
- 2021
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 127:10
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Tidskriftsartikel (refereegranskat)abstract
- Interferometers are widely used in imaging technologies to achieve enhanced spatial resolution, but require that the incoming photons be indistinguishable. In previous work, we built and analyzed color erasure detectors, which expand the scope of intensity interferometry to accommodate sources of different colors. Here we demonstrate experimentally how color erasure detectors can achieve improved spatial resolution in an imaging task, well beyond the diffraction limit. Utilizing two 10.9-mm- aperture telescopes and a 0.8 m baseline, we measure the distance between a 1063.6 and a 1064.4 nm source separated by 4.2 mm at a distance of 1.43 km, which surpasses the diffraction limit of a single telescope by about 40 times. Moreover, chromatic intensity interferometry allows us to recover the phase of the Fourier transform of the imaged objects-a quantity that is, in the presence of modest noise, inaccessible to conventional intensity interferometry.
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| 5. |
- Qu, Luo-Yuan, et al.
(författare)
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Chromatic interferometry with small frequency differences
- 2020
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Ingår i: Optics Express. - 1094-4087. ; 28:22, s. 32294-32301
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Tidskriftsartikel (refereegranskat)abstract
- By developing a 'two-crystal' method for color erasure, we can broaden the scope of chromatic interferometry to include optical photons whose frequency difference falls outside of the 400 nm to 4500 nm wavelength range, which is the passband of a PPLN crystal. We demonstrate this possibility experimentally, by observing interference patterns between sources at 1064.4 nm and 1063.6 nm, corresponding to a frequency difference of about 200 GHz.
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| 6. |
- Qu, Luo-Yuan, et al.
(författare)
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Color Erasure Detectors Enable Chromatic Interferometry
- 2019
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 123:24
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Tidskriftsartikel (refereegranskat)abstract
- By engineering and manipulating quantum entanglement between incoming photons and experimental apparatus, we construct single-photon detectors which cannot distinguish between photons of very different wavelengths. These color-erasure detectors enable a new kind of intensity interferometry, with potential applications in microscopy and astronomy. We demonstrate chromatic interferometry experimentally, observing robust interference using both coherent and incoherent photon sources.
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