Dense Coding for Continuous Variables

Masashi Ban

Xiaoping Lou, Hu Long, Wensheng Tang +2 more

Motivated by the dense coding and teleportation of two-mode squeezed vacuum (TMSV) state, a continuous-variable arbitrated quantum signature (CV-AQS) scheme is proposed. The signer Alice generates the signature by the dense coding and sends it to the verifier Bob. The measurement results of two quadrature components serve for the recovery of the secret message. With the help of the arbitrator Charlie, Bob verifies the validity of the signature. The security of the presented protocol is protected by the calculation of the fidelity parameter and the implementation process of two-mode squeezed vacuum (TMSV) state teleportation. Moreover, the proposed scheme can be correctly implemented in the lossy and lossless transmission with a higher capacity.

Roger Alfredo Kögler, Leonardo Neves

Timothy C. Ralph, Elanor H. Huntington

We investigate the conditions under which unconditional dense coding can be achieved using continuous-variable entanglement. We consider the effect of entanglement impurity and detector efficiency and discuss experimental verification. We conclude that the requirements for a strong demonstration are not as stringent as previously thought, and are within the reach of present technology.

Liping Lin, Chun-Hui Huang

Mrinmoy Samanta, Ayan Patra, Rivu Gupta +1 more

We analyze the continuous variable (CV) dense coding protocol between a single sender and a single receiver when affected by noise in the shared and encoded states, as well as when the decoding is imperfect. We present a formalism to derive the dense coding capacity (DCC) of generic two-mode Gaussian states when affected by Gaussian noise models. When the constituent modes are affected by quantum-limited amplifiers, pure-loss channels, and environmental interactions, together with an inefficient decoding mechanism comprising imperfect double-homodyne detection, we specifically investigate the performance of the two-mode squeezed vacuum state (TMSV) by varying the strength of the noise. Through numerical simulations, we further show that the negative conditional entropy may be used to assess the quantum advantage of CV dense coding in Gaussian setups. While comparing the TMSV with other Gaussian states, we identify a class of pure Gaussian states capable of furnishing a capacity equal to that of the TMSV, under equal energy constraints in the ideal regime. Further, we demonstrate that, while the TMSV state is more susceptible to noise, it still provides the maximum quantum advantage in the DC protocol under practical conditions.