arXiv subjects

Hiroki Takahashi

Publications and source records attributed to Hiroki Takahashi.

58 records · Page 4Linked to original sources

arXiv2008

Generation of large-amplitude coherent-state superposition via ancilla-assisted photon-subtraction

We propose and demonstrate a novel method to generate a large-amplitude coherent-state superposition (CSS) via ancilla-assisted photon-subtraction. The ancillary mode induces quantum interference of indistinguishable processes, widening the controllability of quantum superposition at the conditional output. We demonstrate the concept in the time domain, by a simple time-separated two-photon subtraction from cw squeezed light. We observe the largest CSS ever reported without any corrections, which will enable various quantum information applications with CSS states.

quant-ph↗

arXiv2008

Large amplitude coherent state superposition generated by a time-separated two-photon subtraction from a continuous wave squeezed vacuum

Theoretical analysis is given for a two-photon subtraction from a continuous wave (CW) squeezed vacuum with finite time separation between two detection events. In the CW photon subtraction process, the generated states are inevitably described by temporal mutimode states. Our approach is based on Schrödinger picture which provides mathematically simple forms and an intuitive understanding of its multimode structure. We show that, in our process, the photon subtracted squeezed vacuum is generated in two temporal modes and one of these modes acts as an ancillary mode to make the other one a large amplitude coherent state superposition.

quant-ph↗

arXiv2008

Temporally multiplexed superposition states of continuous variables

We study non-Gaussian states generated by two-photon subtraction from a cw squeezed light source. In a cw scheme one can subtract two photons from the source with a designated time separation and can genarate temporally multiplexed superposition states of continuous variables. We numerically study the properties of these states in the light of bosonic interference in the time domain. In an appropriate temporal mode amplified kittens are produced in a region where the time separation is comparable with the correlation time of squeezed packets.

quant-ph↗

arXiv2005

Demonstration of quantum telecloning of optical coherent states

Quantum cryptography promises in-principle secure communication between two parties via a quantum channel, with the ability to discover eavesdropping when it occurs. In 1999, a telecloning protocol was invented [M. Murao {\it et al}., Phys. Rev. A {\bf 59}, 156 (1999)] that provides a way for an eavesdropper to remotely monitor a quantum cryptographic channel such that even if eavesdropping is discovered, the identity and location of the eavesdropper is guaranteed uncompromised. Here we demonstrate unconditional telecloning experimentally for the first time. We symmetrically teleclone coherent states of light, achieving a fidelity for each clone of $F = 0.58 \pm 0.01$.

quant-ph↗