Abstract: Systems and methods for obtaining information on a key in the BB84 (Bennett-Brassard 1984) protocol of quantum key distribution are provided. A representative system comprises a quantum cryptographic entangling probe, comprising a single-photon source configured to produce a probe photon, a polarization filter configured to determine an initial probe photon polarization state for a set error rate induced by the quantum cryptographic entangling probe, a quantum controlled-NOT (CNOT) gate configured to provide entanglement of a signal with the probe photon polarization state and produce a gated probe photon so as to obtain information on a key, a Wollaston prism configured to separate the gated probe photon with polarization correlated to a signal measured by a receiver, and two single-photon photodetectors configured to measure the polarization state of the gated probe photon.

Abstract: An alternative design is given for an optimized quantum cryptographic entangling probe for attacking the BB84 protocol of quantum key distribution. The initial state of the probe has a simpler analytical dependence on the set error rate to be induced by the probe than in the earlier design. The new device yields maximum information to the probe for a full range of induced error rates. As in the earlier design, the probe contains a single CNOT gate which produces the optimum entanglement between the BB84 signal states and the correlated probe states.

Abstract: Systems and methods for obtaining information on a key in the BB84 (Bennett-Brassard 1984) protocol of quantum key distribution are provided. A representative system comprises a quantum cryptographic entangling probe, comprising a single-photon source configured to produce a probe photon, a polarization filter configured to determine an initial probe photon polarization state for a set error rate induced by the quantum cryptographic entangling probe, a quantum controlled-NOT (CNOT) gate configured to provide entanglement of a signal with the probe photon polarization state and produce a gated probe photon so as to obtain information on a key, a Wollaston prism configured to separate the gated probe photon with polarization correlated to a signal measured by a receiver, and two single-photon photodetectors configured to measure the polarization state of the gated probe photon.

Abstract: An alternative design is given for an optimized quantum cryptographic entangling probe for attacking the BB84 protocol of quantum key distribution. The initial state of the probe has a simpler analytical dependence on the set error rate to be induced by the probe than in the earlier design. The new device yields maximum information to the probe for a full range of induced error rates. As in the earlier design, the probe contains a single CNOT gate which produces the optimum entanglement between the BB84 signal states and the correlated probe states.

Abstract: Quantum key distribution (QKD) employs non-orthogonal quantum states to distribute a random bit sequence between two users for use as a provably secure key for encryption and authentication. The key generation procedure involves the transmission, interception, and reception of two nonorthogonal photon polarization states. At the receiving end, a positive-operator-valued measure (POVM) is employed in the measurement process. The invention is a receiver that is an all-optical realization of the POVM and includes a Wollaston prism, a mirror, two beam splitters, a polarization rotator, and three photodetectors.

Abstract: A simple method and apparatus are disclosed for producing high power gigat level millimeter radiation from an intensely oscillating relativistic turbulent electron plasma created in and beyond the gap of a high voltage diode configuration. The diode is comprised of an explosive cathode emitter and an extended anode structure connected to the inner and outer conductors, respectively, of a high voltage pulse line under conditions of space charge saturation. The gap spacing and voltage determine the dominate mode of the turbulent longitudinal waves which are directly converted into free transverse waves polarized parallel to the electron beam. A simple coaxial reflector-antenna system is also utilized to direct and focus the resultant radiation.