Two schemes of projection measurement are realized experimentally to demonstrate the de Broglie wavelength of three photons without the need for a maximally entangled three-photon state (the NOON state). The first scheme is based on the proposal by Wang and Kobayashi (Phys. Rev. A {\bf 71}, 021802) that utilizes a couple of asymmetric beam splitters while the second one applies the general method of NOON state projection measurement to three-photon case. Quantum interference of three photons is responsible for projecting out the unwanted states, leaving only the NOON state contribution in these schemes of projection measurement.
Recently, a new interpretation of quantum mechanics has been developed for the wave nature of a photon, where determinacy in quantum correlations becomes an inherent property without the violation of quantum mechanics. Here, we experimentally demonstrate a direct proof of the wave natures of quantum correlation for the so-called coherence de Broglie waves (CBWs) using sub-Poisson distributed coherent photon pairs obtained from an attenuated laser. The observed experimental data coincides with the analytic solutions and the numerical calculations. Thus, the CBWs pave a road toward deterministic…
A technique is demonstrated that allows free space atomic fountain clocks and interferometers to utilize optical cavity generated spin-squeezed states with over $390\,000$ ${}^{87}\text{Rb}$ atoms. Fluorescence imaging is used for population spectroscopy, after a free fall time of 4 milliseconds, to resolve a single-shot phase sensitivity of $814 (61)$ microradians, which is $5.8(0.6)$ decibels (dB) below the quantum projection limit. The dynamic range is observed to be 100 milliradians. When operating as a microwave atomic clock with $240\,000$ atoms at a 3.6 ms Ramsey time, a single-shot fra…
We report an experimental investigation of the role of measurement in quantum metrology when the states of the probes are mixed. In particular, we investigated optimized local measurements and general global projective measurements, involving entangling operations, on noisy Werner states of polarization entangled photons. We demonstrate experimentally that global measurement presents an advantage in parameter estimation with respect to the optimized local strategy. Moreover, the global strategy provides unambiguous information about the parameter of interest even when the amount of noise is no…
Now that fundamental quantum principles of indeterminacy and measurement have become the basis of new technologies that provide secrecy between two communicating parties, there is a need to provide teaching laboratories that illustrate how these technologies work. In this article we describe a laboratory exercise in which students perform quantum key distribution with single photons, and see how the secrecy of the communication is ensured by the principles of quantum superposition and state projection. We used a table-top apparatus, similar to those used in correlated-photon undergraduate labo…
Orbital Angular Momentum embedded Einstein Podolsky Rosen Entanglement Generated from Cold Atoms
Einstein Podolsky Rosen（EPR）纠缠量子态不仅在量子力学的基础研究中具有重要意义，而且在量子信息的信息处理中也具有重要意义。以前的EPR纠缠态演示是用等相位波前的光子构建的。更复杂的情况下，结构化的波前还没有被调查。在这里，我们报告的第一个实验演示的EPR纠缠光子对携带轨道角动量（OAM）信息，导致OAM嵌入EPR纠缠态。我们测量了投影下的鬼干涉对相对相位的依赖性的动力学。另外，在OAM和EPR位置动量空间中重构的矩阵在高维中表现出特殊的超纠缠。
In this work, we present a quantum secret sharing scheme based on Bell state entanglement and sequential projection measurements. The protocol verifies the $n$ out of $n$ scheme and supports the aborting of the protocol in case all the parties do not divulge in their valid measurement outcomes. The operator-qubit pair forms an integral part of the scheme determining the classical secret to be shared. The protocol is robust enough to neutralize any eavesdropping on a particular qubit of the dealer. The experimental demonstration of the scheme is done on IBM-QE cloud platform with backends \text…
