Physics Plus Randomness

Woong Son, Han Seung Jang, Bang Chul Jung

In this paper, we propose a pseudo-random beamforming (PRBF) technique for improving physical-layer security (PLS) in multiple input multiple output (MIMO) downlink cellular networks consisting of a legitimate base station (BS), multiple legitimate mobile stations (MSs) and potential eavesdroppers. The legitimate BS can obtain available potential eavesdroppers’ channel state information (CSI), which is registered in an adjacent cell. In the proposed PRBF technique, the legitimate BS pseudo-randomly generates multiple candidates of the transmit beamforming (BF) matrix, in which each transmit BF matrix consists of multiple orthonormal BF vectors and shares BF information with legitimate MSs before data transmission. Each legitimate MS generates receive BF vectors to maximize the receive signal-to-interference-plus-noise (SINR) for all pseudo-randomly generated transmit beams and calculates the corresponding SINR. Then, each legitimate MS sends a single beam index and the corresponding SINR value of the BF vector that maximizes the received SINR for each BF matrix since a single spatial stream is sent to each legitimate MS. Based on the feedback information from legitimate MSs and the CSI from the legitimate BS to eavesdroppers, the legitimate BS selects the optimal transmit BF matrix and the legitimate MSs that maximizes secrecy sum-rate. We also propose a codebook-based opportunistic feedback (CO-FB) strategy to reduce feedback overhead at legitimate MSs. Based on extensive computer simulations, the proposed PRBF with the proposed CO-FB significantly outperforms the conventional random beamforming (RBF) with the conventional opportunistic feedback (O-FB) strategies in terms of secrecy sum-rate and required feedback bits.

Виктор Степанович Доценко

David Z. Albert

Aram W. Harrow, Patrick M. Hayden, Debbie Leung

We describe a method for nonobliviously communicating a 2l-qubit quantum state by physically transmitting l+o(l) qubits, and by consuming l ebits of entanglement plus some shared random bits. In the nonoblivious scenario, the sender has a classical description of the state to be communicated. Our method can be used to communicate states that are pure or entangled with the sender's system; l+o(l) and 3l+o(l) shared random bits are sufficient, respectively.

Alberto Alejandro Duarte

This deposit contains the manuscript and complete supplementary material supporting the hardware realization of binary Clifford quantum random access codes for the sectors n=4 and n=5 on the IBM Heron r2 processor ibm_kingston. A quantum random access code encodes n classical bits into a single quantum carrier so that any one bit can later be recovered with bias above one half. The sectors n=2 and n=3 are realized natively in the qubit Bloch sphere; the sectors with n greater than or equal to four require Hilbert-space dimension at least four and are realized here using mutually anticommuting Hermitian generators of the Clifford algebra. For n=4 and n=5 this places the encoding in dimension four, implemented on two physical qubits. The experiment covers all 64 input-query configurations of the n=4 sector and all 160 configurations of the n=5 sector, with 8192 shots per configuration and no error mitigation applied. The measured per-sector biases are 0.469 plus or minus 0.002 for n=4, against the predicted value of 0.500, and 0.432 plus or minus 0.002 for n=5, against the predicted value of approximately 0.447

J. H. Beynon