Unidimensional Continuous-Variable Quantum Key Distribution with Untrusted Detection under Realistic Conditions

Abstract

A unidimensional continuous-variable quantum key distribution protocol with untrusted detection is proposed, where the two legitimate partners send unidimensional modulated or Gaussian-modulated coherent states to an untrusted third party, i.e., Charlie, to realize the measurement. Compared with the Gaussian-modulated coherent-state protocols, the unidimensional modulated protocols take the advantage of easy modulation, low cost, and only a small number of random numbers required. Security analysis shows that the proposed protocol cannot just defend all detectors side channels, but also achieve great performance under certain conditions. Specifically, three cases are discussed in detail, including using unidimensional modulated coherent states in Alice’s side, in Bob’s side, and in both sides under realistic conditions, respectively. Under the three conditions, we derive the expressions of the secret key rate and give the optimal gain parameters. It is found that the optimal performance of the protocol is achieved by using unidimensional modulated coherent states in both Alice’s and Bob’s side. The resulting protocol shows the potential for long-distance secure communication using the unidimensional quantum key distribution protocol with simple modulation method and untrusted detection under realistic conditions.

Security analysis of unidimensional continuous-variable quantum key distribution with discretized amplitude modulation

“…In addition, the unidimensional continuous variable measurementdevice-independent QKD (CV-MDI QKD) protocol [23] and the unidimensional two-way CVQKD protocol [24] were proposed to simplify the system realization. The imperfect implementation of UD-CVQKD was studied in [25,26], and the improvements of UD-CVQKD are also being developed [27][28][29].…”

Countermeasure for Negative Impact of a Practical Source in Continuous-Variable Measurement-Device-Independent Quantum Key Distribution

“…To solve this, some assumptions that the devices are trustworthy are removed to meet the realistic conditions, and various device-independent or partial-device-independent protocols have been proposed, including CV measurementdevice-independent (MDI) protocol [30][31][32], which can defend all the attacks against measurement device. Due to this great ability, CV-MDI QKD protocol has attained a lot of progress in theory [33][34][35][36] and has been experimentally demonstrated in lab [30], making a common scenario in communication possible where two users can only be connected through an untrusted third party. The detectors in the measurement side are not easy to attack in the CV-MDI QKD system, and, relatively speaking, the sources are fragile [37][38][39][40][41][42] due to the gap between the practical laser and the ideal assumption.…”

Long-distance continuous-variable measurement-device-independent quantum key distribution with postselection

“…Unfortunately, developing a protocol that allows exploitation of the practicality of the CV MDI regime at long distance is a difficult problem in recent QKD theory [36][37][38][39]. A great deal of effort has been directed at improving the performance of this type of protocol, with proposals based on virtual photon subtraction [40,41], unidimensional modulation [42], or discrete modulation [43]. While these protocols offered an improvement in the range of the asymmetric configuration, in which the relay is positioned within close range of one of the parties, their applicability in the symmetric configuration, in which the relay is positioned equidistance between the parties, was very limited.…”