6 citations · 17 across the 5 of their papers we have counts for
7 papers
On the Matrix Representation of Quantum Operations
Yoshihiro Nambu, Kazuo Nakamura
This paper considers two frequently used matrix representations -- what we call the - and -matrices -- of a quantum operation and their applications. The matrices d…
Antinormally Ordered Photodetection of Continuous-mode Field
Koji Usami, Akihisa Tomita, Kazuo Nakamura
When the electromagnetic field is detected by stimulated emission, rather than by absorption, antinormally ordered photodetection can be realized. One of the distinct features of t…
Measured Quantum Fourier Transform of 1024 Qubits on Fiber Optics
Akihisa Tomita, Kazuo Nakamura
Quantum Fourier transform (QFT) is a key function to realize quantum computers. A QFT followed by measurement was demonstrated on a simple circuit based on fiber-optics. The QFT wa…
Planar lightwave circuits for quantum cryptographic systems
Yoshihiro Nambu, Takaaki Hatanaka, Kazuo Nakamura
We propose a quantum cryptographic system based on a planar lightwave circuit (PLC) and report on optical interference experiments using PLC-based unbalanced Mach-Zehnder interfero…
Single-photon interference experiment over 100 km for quantum cryptography system using a balanced gated-mode photon detector
Hideo Kosaka, Akihisa Tomita, Yoshihiro Nambu +2
We demonstrate single-photon interference over 100 km using a balanced gated-mode photon detector and a plug & play system for quantum key distribution. The visibility with 0.1 pho…
Entangled Nonorthogonal States and Their Decoherence Properties
Osamu Hirota, Steven J. van Enk, Kazuo Nakamura +2
This paper presents properties of the so-called quasi-Bell states: entangled states written as superpositions of nonorthogonal states. It is shown that a special class of those sta…