Abstract:Measuring an entangled state of two particles is crucial to many quantum communication protocols. Yet Bellstate distinguishability using a finite apparatus obeying linear evolution and local measurement is theoretically limited. We extend known bounds for Bell-state distinguishability in one and two variables to the general case of entanglement in n two-state variables. We show that at most 2 n+1 − 1 classes out of 4 n hyper-Bell states can be distinguished with one copy of the input state. With two copies, co… Show more
“…This Equation relates the maximun number of distinguishable Bell-state classes of two photons, entangled in n dichotomic degrees of freedom, in experiments in which the two photons are not mixed at the device, with the number of ZPF inputs at the source of entanglement and inside the analyser. In the standard Hilbert space approach, given to the fact that the first detection event, which is produced in one of the 2 n detectors of the left (or right) area, does not give any information about the Bell-state of the two photons, the second detection event can discriminate to 2 n sets of Bell states [31]. From the WRHP approach, this quantity can be obtained by subtracting the total number of idle channels at the analyser, N ic , from the total number of ZPF sets of modes that are amplified at the source of hyperentanglement, N ZP F,S .…”
Section: Zpf and Complete Bsm In The Rome Experimentsmentioning
AcknowledgementsThe authors would like to thank Prof. E. Santos for revising the manuscript, and for helpful suggestions and comments on the work. We are grateful for the insights gained in conversations with R. Risco-Delgado.
AbstractThe Wigner representation of parametric down conversion in the Heisenberg picture is applied to the study of the Rome teleportation experiment. We investigate the physical meaning of the zeropoint inputs at the different areas of the experimental setup. In particular, we establish a quantitative relationship between the zeropoint sets of modes that are needed for the preparation of the quantum state to be teleported, the idle channels inside the one-photon polarization-momentum Bell-state analyser, and the possibility of performing teleportation of a polarization state whith certainty. arXiv:1707.09624v1 [quant-ph] 30 Jul 2017 degrees of freedom (polarization or momentum) of Alice's photon [15]. The other photon of the down converted pair is sent to Bob. The advantage of this teleportation scheme is that a complete BSM of one-photon polarizationmomentum Bell-states is possible. Nevertheless, the input state cannot be supplied by an external system, and this presents some limitations, such as the inability to teleport entangled or mixed states [2]. The result obtained by Alice is communicated to Bob, who uses this information to apply one out of four unitary transformations, in order to reproduce the original state. This experiment was proposed by Popescu [20] and performed in Rome [15] by using two-photon momentum entanglement, and polarization coding for preparing the qubit to be teleported. The Innsbruck and Rome experiments omitted the final stage of teleportation, the unitary transformations applied by Bob after the classical communication in order to reconstruct the unknown state. This was accomplished using nuclear magnetic resonance [21], and later the first long-distance optical quantum teleportation experiment with active feed-forward in real time was accomplished [22].The Wigner representation of quantum optics in the Heisenberg picture (WRHP) has been applied in recent years to the study of experiments on quantum communication using photons generated via parametric down conversion. The WRHP formalism of PDC resembles nonlinear classical optics, by taking into consideration the vacuum inputs at the nonlinear crystal and the different linear optical devices placed between the source of down converted photons and the detectors. The zeropoint field (ZPF) appears as a stochastic field that couples with the laser beam into the crystal, giving rise to the down converted beams [23,24]. In this way, the signals emitted by the crystal constitute needles of radiation generated by the amplification of vacuum fluctuations [25]. These signals propagate according to the classical Maxwell equations, so that the WRHP formalism of PDC emphasizes the wave-like aspects in the generation and propagation of light [26]. The Wigner function of PDC is positive, and corresponds to the Gaussian Wi...
“…This Equation relates the maximun number of distinguishable Bell-state classes of two photons, entangled in n dichotomic degrees of freedom, in experiments in which the two photons are not mixed at the device, with the number of ZPF inputs at the source of entanglement and inside the analyser. In the standard Hilbert space approach, given to the fact that the first detection event, which is produced in one of the 2 n detectors of the left (or right) area, does not give any information about the Bell-state of the two photons, the second detection event can discriminate to 2 n sets of Bell states [31]. From the WRHP approach, this quantity can be obtained by subtracting the total number of idle channels at the analyser, N ic , from the total number of ZPF sets of modes that are amplified at the source of hyperentanglement, N ZP F,S .…”
Section: Zpf and Complete Bsm In The Rome Experimentsmentioning
AcknowledgementsThe authors would like to thank Prof. E. Santos for revising the manuscript, and for helpful suggestions and comments on the work. We are grateful for the insights gained in conversations with R. Risco-Delgado.
AbstractThe Wigner representation of parametric down conversion in the Heisenberg picture is applied to the study of the Rome teleportation experiment. We investigate the physical meaning of the zeropoint inputs at the different areas of the experimental setup. In particular, we establish a quantitative relationship between the zeropoint sets of modes that are needed for the preparation of the quantum state to be teleported, the idle channels inside the one-photon polarization-momentum Bell-state analyser, and the possibility of performing teleportation of a polarization state whith certainty. arXiv:1707.09624v1 [quant-ph] 30 Jul 2017 degrees of freedom (polarization or momentum) of Alice's photon [15]. The other photon of the down converted pair is sent to Bob. The advantage of this teleportation scheme is that a complete BSM of one-photon polarizationmomentum Bell-states is possible. Nevertheless, the input state cannot be supplied by an external system, and this presents some limitations, such as the inability to teleport entangled or mixed states [2]. The result obtained by Alice is communicated to Bob, who uses this information to apply one out of four unitary transformations, in order to reproduce the original state. This experiment was proposed by Popescu [20] and performed in Rome [15] by using two-photon momentum entanglement, and polarization coding for preparing the qubit to be teleported. The Innsbruck and Rome experiments omitted the final stage of teleportation, the unitary transformations applied by Bob after the classical communication in order to reconstruct the unknown state. This was accomplished using nuclear magnetic resonance [21], and later the first long-distance optical quantum teleportation experiment with active feed-forward in real time was accomplished [22].The Wigner representation of quantum optics in the Heisenberg picture (WRHP) has been applied in recent years to the study of experiments on quantum communication using photons generated via parametric down conversion. The WRHP formalism of PDC resembles nonlinear classical optics, by taking into consideration the vacuum inputs at the nonlinear crystal and the different linear optical devices placed between the source of down converted photons and the detectors. The zeropoint field (ZPF) appears as a stochastic field that couples with the laser beam into the crystal, giving rise to the down converted beams [23,24]. In this way, the signals emitted by the crystal constitute needles of radiation generated by the amplification of vacuum fluctuations [25]. These signals propagate according to the classical Maxwell equations, so that the WRHP formalism of PDC emphasizes the wave-like aspects in the generation and propagation of light [26]. The Wigner function of PDC is positive, and corresponds to the Gaussian Wi...
“…The measurements required for QT are probabilistic when using linear optics; this problem is worsened when teleporting higher-dimensional states. Because the percentage of the total higher-dimensional Bell states discriminated with linear optics detection decreases as dimension increases, QT of states d42 is impossible to do with perfect fidelity without nonlinear interactions 31,32 . Furthermore, although RSP can be performed deterministically for any state dimension, the complexity of the measurement increases quadratically with the state dimension: a d-dimensional state with 2d-2 state parameters requires a POVM with d 2 outputs and detectors.…”
Transmitting quantum information between two remote parties is a requirement for many quantum applications; however, direct transmission of states is often impossible because of noise and loss in the communication channel. Entanglement-enhanced state communication can be used to avoid this issue, but current techniques require extensive experimental resources to transmit large quantum states deterministically. To reduce these resource requirements, we use photon pairs hyperentangled in polarization and orbital angular momentum to implement superdense teleportation, which can communicate a specific class of single-photon ququarts. We achieve an average fidelity of 87.0(1)%, almost twice the classical limit of 44% with reduced experimental resources than traditional techniques. We conclude by discussing the information content of this constrained set of states and demonstrate that this set has an exponentially larger state space volume than the lower-dimensional general states with the same number of state parameters.
“…However, completely analysis of the hyperentangled Bell-state is still a huge challenge in high-capacity quantum information processing. Considering that completely HBSA cannot be accomplished only with linear optical elements [39,40], researchers have gradually introduced nonlinear media [41][42][43][44][45][46][47][48] to assist complete HBSA. In 2010, Sheng et al [41] firstly presented a way to completely distinguish the 16 hyperentangled Bell states completely with cross-Kerr nonlinearity, and discussed its application in quantum hyperteleportation and hyperentanglement swapping.…”
Hyperentangled Bell-state analysis (HBSA) is critical for high-capacity quantum communication. Based on a recent proposal by Wang et al. [Opt. Express 24 28444-28458 (2016)]. We design two separate schemes for error-heralded deterministic generation and self-assisted complete HBSA of two-photon entangled in both polarization and spatial-mode degrees of freedom. Different from previous programs, we firstly proposed an error-heralded block with a singly charged quantum dot inside a single-sided optical microcavity, with which errors due to imperfect interactions between photons and quantum dot systems can be heralded. Thanks to the error-heralded block, the fidelity of the two schemes for hyperentangled Bell-state generation and complete HBSA can reach unit one. Besides, hyperentanglement makes it possible to analyze the polarization state assisted by the measured spatial-mode state. The self-assisted way of the HBSA greatly simplifies the analysis process and largely relaxes the requirements on nonlinearities. Therefore, the schemes hold the promise to implement more easily in experiments, taking a step closer to the long-distance high-capacity quantum communication.
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