p-Adic Path Integrals for Quadratic Actions

The Feynman path integral in p-adic quantum mechanics is considered. The probability amplitude ${\cal K}_p (x^{\prime\prime},t^{\prime\prime}; x^\prime,t^\prime)$ for one-dimensional systems with quadratic actions is calculated in an exact form, which is the same as that in ordinary quantum mechanics.Comment: 9 page

Performance Improvement of QPSK Signal Predetection EGC Diversity Receiver

This paper proposes a modification of quadrature phase-shift-keying (QPSK) signal diversity reception with predetection equal gain combiner (EGC). The EGC combining is realized by using the constant modulus algorithm (CMA). Carrier synchronization is performed by the phase locked loop (PLL). Comparative analysis of the modified and ordinary diversity receiver in the presence of carrier frequency offset in the additive white Gaussian noise (AWGN) channel, as well as in Rician fading channel is shown. The proposed diversity receiver allows significant frequency offset compared to the diversity receiver that uses only PLL, and the error probability of the proposed receiver is very close to the error probability of the receiver with only PLL and zero frequency offset. The functionality of the proposed diversity receiver, as well as its properties is experimentally verified on a system based on universal software radio peripheral (USRP) hardware. The performed comparison confirms the expected behavior of the system

Proposal for Slepian-States-Based DV- and CV-QKD Schemes Suitable for Implementation in Integrated Photonics Platforms

Quantum key distribution (QKD) leverages underlying principles of quantum mechanics to realize distribution of keys with verifiable security. Despite appealing features of QKD, there are some fundamental and technical challenges that need to be solved prior to its widespread applications. First, QKD secret-key rate (SKR) is fundamentally limited by channel loss, as dictated by the rate-loss tradeoff. Quantum repeaters would be an ultimate solution to overcome this problem; however, they are well beyond the reach. The second challenge lies in the scalability and cost. Future's QKD systems must be suitable for mass production with low cost, reliable realignment-free operations, and small power consumption. To solve for these problems in a simultaneous manner, we propose to encode information in the orthogonal Slepian sequences' bases. Such an approach is highly robust against turbulence effects in free-space optical links and dispersion effects/fiber non-linearities in fiber-optics channels, thereby improving QKD distance. Moreover, exploiting multidimensional encoding space enables high spectral efficiency QKD so that the SKR can be significantly improved. Critically, generation, processing, and detection of Slepian states can be reliably implemented in an integrated quantum photonics platform, based on both reflective and transmissive waveguide Bragg gratings (WBGs). Proposed reflective/transmissive WBG-based Slepian states are applicable to both discrete variable and continuous variable QKD systems.Multidisciplinary University Research Initiatives Office of Naval Research [N00014-13-1-0627]; National Science FoundationOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Applications of Laser Light Probes to Quantitative Sensing Stress Waves

The recent development of laser light probes for stress wave measurements has aided our understanding of acoustic emission and ultrasonic signals by allowing quantitative measurements of stress waveforms. This paper reports on applications of the laser interferometer probe for surface detection of stress waves and the laser transmission probe for sensing of stress waves inside transparent materials. Laser light probes were used to characterize ultrasonic and acoustic emission transducers\u27 response in a realistic configuration, with transducers in actual contact with a solid. Laser light probes also were applied in directly detecting acoustic emission due to stress corrosion cracking in 7039 aluminum and crazing of Plexiglass. The results of the laser light probe measurements indicate that conventional piezoelectric transducers, although adequate for many ultrasonic pulse inspection tests, are severely limited as stress pulse sensors for acoustic emission measurements. The acoustic emission signals measured by the laser light probe showed a pulse-like waveform which has not been previously recorded by conventional piezoelectric acoustic emission sensors

On the Discretized Gaussian Modulation (DGM)- Based Continuous Variable-QKD

To overcome the low reconciliation efficiency problem of Gaussian modulation (GM)-basedcontinuous variable (CV)-quantum key distribution (QKD), in this paper, we propose to use discretized GM (DGM)-based-CV-QKD. The proposed CV-QKD scheme has complexity and reconciliation efficiency similar to that of discrete modulation (DM)-based-CV-QKD and at the same time solves for the problem of the nonexistence of strict security proofs for the DM-CV-QKD under the collective attacks. We demonstrate that the 32-points-based DGM CV-QKD can closely approach the theoretical SKR-limit in medium and high channel losses regimes. On the other hand, the 64-points-based DGM CV-QKD scheme closely approaches the SKR-limit for all channel losses.ONR MURI program [N00014-13-1-0627]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Optimized-Eight-State CV-QKD Protocol Outperforming Gaussian Modulation Based Protocols

In this paper, an optimized-eight-state CV-QKD protocol is proposed significantly outperforming previously introduced discrete modulation (DM) protocols as well as the corresponding Gaussian modulation (GM)-based CV-QKD protocols for practical reconciliation efficiencies values in terms of both secret-key rate (SKR) and achievable distance. The proposed CV-QKD protocol also outperforms, in terms of SKR, the corresponding high-cost single-photon DV-QKD scheme, employing an array of multiplexed single-photon detectors, for several orders of magnitude. We also describe a generalized RF-assisted CV-QKD scheme with heterodyne detection applicable to arbitrary DM scheme, insensitive to the laser phase noise and frequency offset fluctuations.Multidisciplinary University Research Initiative (MURI) Office of Naval Research (ONR) [N00014-13-1-0627]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]