We present the results of a new experimental study of the quantum entanglement of photon pairs produced in positron-electron annihilation at rest. The experimental setup includes a system of Compton polarimeters to measure the Compton scattering of annihilation photons in entangled and decoherent states. Decoherent states are prepared by pre-scattering of one of the initial photons prior to measurements in polarimeters. For the first time, a direct comparison of the polarization correlations of annihilation photons in the entangled and thus prepared separable states has been carried out. The angular distributions of scattered photons turned out to be the same in both quantum states, which is an unexpected discovery for the quantum-entangled positron emission tomography. Moreover, the correlation function in the Bell's inequality is also the same for entangled and separable states. It follows that, despite numerous measurements in a series of experiments, there is still no experimental proof of the entanglement of annihilation photons. These results are in line with recent theoretical predictions of an identical Compton scattering cross-section for entangled and specific mixed separable quantum states and cast doubt on the universality of the Bell's theorem for testing the entanglement and nonlocality in quantum theory.
The differential cross-section of the single-photon annihilation of channeled positron on the K-shell electron of one of the crystal atoms is calculated and angular distribution of emitted photons is investigated. It is shown that cross-section has a complicated dependence on positron entrance angle with respect to crystal plane. It is demonstrated that this orientation dependence is different for different positron transverse energy levels. The dependence of the differential cross-section on the electron longitudinal energy is studied.
The two-photon annihilation of a positron with an electron bound in the 1s state of a H-like ion is calculated within the fully relativistic QED framework. The interaction with the nucleus is treated nonperturbatively, thus allowing the calculations to be carried out for the annihilation with strongly-bound inner shells of heavy ions. Infrared divergences, appearing when one of the emitted photons approaches the low-frequency limit, are accurately eliminated from final expressions. The total cross section of the two-photon and one-photon annihilation processes are compared for a wide range of …
This theoretical research aims to examine areas of the Compton cross section of entangled annihilation photons for the purpose of testing for possible break down of theory, which could have consequences for predicted optimal capabilities of Compton PET systems.We provide maps of the cross section for entangled annihilation photons for experimental verification.We introduce a strategy to derive cross sections in a relatively straight forward manner for the Compton scattering of a hypothetical separable, mixed and entangled states. To understand the effect that entanglement has on the cross sect…
An experimental setup for studying the Compton scattering of annihilation photons in various (entangled and decoherent) quantum states is presented. Two entangled $γ$-quanta with an energy of 511 keV and mutually orthogonal polarizations are produced by positron-electron annihilation in a thin aluminum plate and are emitted in opposite directions. To measure both photons, the setup provides two equivalent arms of Compton polarimeters. A Compton polarimeter consists of a plastic scintillation scatterer and an array of NaI(Tl) detectors for measuring photons deflected at an angle of 90$^\circ$. …
Coupling a many-body system to a thermal environment typically destroys the quantum coherence of its state, leading to an effective classical dynamics at the longest time scales. We show that systems with anyon-like defects can exhibit universal late-time dynamics that is stochastic, but fundamentally non-classical, because some of the quantum information about the state is topologically protected from the environment. Our coarse-grained model describes one-dimensional systems with domain-wall defects carrying Majorana modes. These defects undergo Brownian motion due to coupling with a bath. S…
We have calculated the expectation values of the spin and the intrinsic magnetic moment of the gamma photons created as a result of the electron-positron annihilation. We show that, depending on its helicity a gamma photon propagating in z direction with an angular frequency carries a magnetic moment of along the propagation direction. Here the (+) and (-) signs stand for the right hand and left circular helicity respectively. e argue that in a Stern-Gerlach experiment (SGE) the magnetic moment is an important property but not the spin of the particles. Because of these two symmetric values of…
We propose a curious protocol for swapping the intra-photon entanglement between path and polarization degrees of freedom of a single photon to inter-photon entanglement between two spatially separated photons which have never interacted. This is accomplished by using an experimental setup consisting of three suitable Mach-Zehnder interferometers along with number of beam splitters, polarization rotators and detectors. Using the same setup, we have also demonstrated an interesting quantum state transfer protocol, symmetric between Alice and Bob. Importantly, the Bell-basis discrimination is no…
The simplest single-photon entanglement is the entanglement of the vacuum state and the single-photon state between two path modes. The verification of the existence of single-photon entanglement has attracted extensive research interests. Here, based on the construction of Bell's inequality in wave space, we propose a new method to verify single photon entanglement. Meanwhile, we define the wave state in two-dimensional space relative to the photon number state, and propose a method to measure it. Strong violation of Bell inequality based on joint measurement of wave states indicates the exis…
Hybrid matter-photon entanglement is the building block for quantum networks. It is very favorable if the entanglement can be prepared with a high probability. In this paper, we report the deterministic creation of entanglement between an atomic ensemble and a single photon by harnessing Rydberg blockade. We design a scheme that creates entanglement between a single photon's temporal modes and the Rydberg levels that host a collective excitation, using a process of cyclical retrieving and patching. The hybrid entanglement is tested via retrieving the atomic excitation as a second photon and pe…
Entanglement is an indispensable quantum resource for quantum information technology. In continuous-variable quantum optics, photon subtraction can increase the entanglement between Gaussian states of light, but for mixed states the extent of this entanglement increase is poorly understood. In this work, we use an entanglement measure based the Rényi-2 entropy to prove that single-photon subtraction increases bipartite entanglement by no more than log 2. This value coincides with the maximal amount of bipartite entanglement that can be achieved with one photon. The upper bound is valid for all…
Quantum Entanglement Degree, Mean Positronium Lifetime, and the $3γ$/$2γ$ Annihilation-Rate Ratio as Novel PET Biomarkers for Hypoxia -- Concept, Challenges, and Predictions
Roadmap Towards Quantum Entanglement Positron Emission Tomography (QE-PET)
Institute of Physics, Jagiellonian University（雅盖隆大学物理研究所）；Center for Theranostics, Jagiellonian University（雅盖隆大学诊疗中心）；University of California Santa Cruz（加州大学圣克鲁兹分校）；Indian Institute of Technology Bombay（印度理工学院孟买分校）；The University of Tokyo（东京大学）；Institute for Medical Research and Occupational Health, Division of Radiation Protection（医学研究与职业健康研究所辐射防护部）；University of Sydney（悉尼大学）；University of Zagreb Faculty of Science, Department of Physics（萨格勒布大学理学院物理系）；ICTP South American Institute for Fundamental Research（ICTP南美基础研究所）；Universidade Federal de São Paulo（圣保罗联邦大学）；Instituto de Fisica Corpuscular (IFIC), CSIC-UV（粒子物理研究所（IFIC），西班牙国家研究委员会-瓦伦西亚大学）；University of Illinois Urbana–Champaign（伊利诺伊大学厄巴纳-香槟分校）；National Institutes for Quantum Science and Technology（国立量子科学技术研究院）；Institute of Science Tokyo（东京科学研究所）
