Abstract
While the objective of conventional quantum key distribution (QKD) is to secretly generate and share the classical bits concealed in the form of maximally mixed quantum states, that of private quantum channel (PQC) is to secretly transmit individual quantum states concealed in the form of maximally mixed states using shared one-time pad and it is called Gaussian private quantum channel (GPQC) when the scheme is in the regime of continuous variables. We propose a GPQC enhanced with squeezed coherent states (GPQCwSC), which is a generalization of GPQC with coherent states only (GPQCo) [Phys. Rev. A 72, 042313 (2005)]. We show that GPQCwSC beats the GPQCo for the upper bound on accessible information. As a subsidiary example, it is shown that the squeezed states take an advantage over the coherent states against a beam splitting attack in a continuous variable QKD. It is also shown that a squeezing operation can be approximated as a superposition of two different displacement operations in the small squeezing regime.
Highlights
While the objective of conventional quantum key distribution (QKD) is to secretly generate and share the classical bits concealed in the form of maximally mixed quantum states, that of private quantum channel (PQC) is to secretly transmit individual quantum states concealed in the form of maximally mixed states using shared one-time pad and it is called Gaussian private quantum channel (GPQC) when the scheme is in the regime of continuous variables
We propose a GPQC enhanced with squeezed coherent states (GPQCwSC), which is a generalization of GPQC with coherent states only (GPQCo) [Phys
We show that GPQCwSC beats the GPQCo for the upper bound on accessible information
Summary
Kabgyun Jeong[1], Jaewan Kim1 & Su-Yong Lee[2] received: 28 January 2015 accepted: 12 August 2015 Published: 14 September 2015. Brádler proposed CV private quantum channel (PQC) using coherent states that are obtained by displacement operations on the vacuum state[14], where he defined a CV maximally mixed state in Gaussian regime and constructed GPQC via the conformation method of coherent states. Brádler’s main proposition is that the Hilbert-Schmidt distance dHS between the CV maximally mixed state and PQC-encryption of arbitrary coherent states is very close for sufficiently large N (N: number of input displacement operations), where Γ N denotes the mixture of all conformations of coherent states that will be defined in Eqs (3) and (4). By arbitrary coherent using the unitary state β : for invariance β and of the CV distance, private we can prove the statement quantum channel N, where is a displaced CV maximally mixed state from b to the position of β.
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