Directionally-Unbiased Unitary Optical Devices in Discrete-Time Quantum Walks
1
Department of Electrical and Computer Engineering, Boston University, 8 Saint Mary’s Street, Boston, MA 02215, USA
2
Department of Physics and Astronomy, Stonehill College, 320 Washington Street, Easton, MA 02357, USA
3
Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA
4
Photonics Center, Boston University, 8 Saint Mary’s Street, Boston, MA 02215, USA
*
Authors to whom correspondence should be addressed.
Entropy 2019, 21(9), 853; https://doi.org/10.3390/e21090853
Received: 30 July 2019 / Revised: 22 August 2019 / Accepted: 29 August 2019 / Published: 31 August 2019
(This article belongs to the Special Issue Quantum Walks and Related Issues)
The optical beam splitter is a widely-used device in photonics-based quantum information processing. Specifically, linear optical networks demand large numbers of beam splitters for unitary matrix realization. This requirement comes from the beam splitter property that a photon cannot go back out of the input ports, which we call “directionally-biased”. Because of this property, higher dimensional information processing tasks suffer from rapid device resource growth when beam splitters are used in a feed-forward manner. Directionally-unbiased linear-optical devices have been introduced recently to eliminate the directional bias, greatly reducing the numbers of required beam splitters when implementing complicated tasks. Analysis of some originally directional optical devices and basic principles of their conversion into directionally-unbiased systems form the base of this paper. Photonic quantum walk implementations are investigated as a main application of the use of directionally-unbiased systems. Several quantum walk procedures executed on graph networks constructed using directionally-unbiased nodes are discussed. A significant savings in hardware and other required resources when compared with traditional directionally-biased beam-splitter-based optical networks is demonstrated.
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Keywords:
quantum walks; linear optics; quantum information processing
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MDPI and ACS Style
Osawa, S.; Simon, D.S.; Sergienko, A.V. Directionally-Unbiased Unitary Optical Devices in Discrete-Time Quantum Walks. Entropy 2019, 21, 853. https://doi.org/10.3390/e21090853
AMA Style
Osawa S, Simon DS, Sergienko AV. Directionally-Unbiased Unitary Optical Devices in Discrete-Time Quantum Walks. Entropy. 2019; 21(9):853. https://doi.org/10.3390/e21090853
Chicago/Turabian StyleOsawa, Shuto; Simon, David S.; Sergienko, Alexander V. 2019. "Directionally-Unbiased Unitary Optical Devices in Discrete-Time Quantum Walks" Entropy 21, no. 9: 853. https://doi.org/10.3390/e21090853
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