Quantum Switchboard with Coupled-Cavity Array

The ability to control the flow of quantum information deterministically is useful for scaling up quantum computation. In this paper, we demonstrate a controllable quantum switchboard which directs the teleportation protocol to one of two targets, fully dependent on the sender’s choice. The quantum switchboard additionally acts as a optimal quantum cloning machine. We also provide a physical implementation of the proposal using a coupled-cavity array. The proposed switchboard can be utilized for the efficient routing of quantum information in a large quantum network.

Unambiguous State Discrimination Attack on the B92 Protocol of Quantum Key Distribution with Single Photons

We consider an unambiguous state discrimination attack on the B92 protocol of quantum key distribution, realized on the basis of polarization encoding of photons produced by a single-photon source. We calculate the secure key rate and the maximal tolerable loss for various overlaps between two signal states employed in this protocol. We make also a comparison with a physically impossible attack of perfect quantum cloning, and show that the unambiguous state discrimination is much more dangerous for the B92 protocol, than this attack, demonstrating thus, that the security of quantum key distribution is not always based on the no-cloning theorem.

High-Dimensiоnаl Quаntum Сlоning

Tries at cloning a quantum tool result in the arrival of imperfections in the nation of the copies. this is a outcome of the no-cloning theorem, that is a vital law of quantum physics and the spine of protection for quantum communications. in spite of the reality that ideal copies are prohibited, a quantum country may be copied with maximal accuracy through severa most top notch cloning schemes. maximum beneficial quantum cloning, which lies at the border of the bodily restrict imposed by way of the no-signaling theorem and the Heisenberg uncertainty principle, has been experimentally found out for low-dimensional photonic states. however, an growth in the dimension-ality of quantum structures is notably beneficial to quantum computation and communication protocols. despite the reality that, no experimental demonstration of most beneficial cloning machines has hitherto been shown for excessive-dimensional quantum systems. We carry out most proper cloning of excessive-dimensional photonic states thru the symmetrization approach. We display the universality of our technique thru carrying out cloning of numerous arbi-trary enter states and really signify our cloning tool with the useful resource of appearing quantum nation tomography on cloned photons. similarly, a cloning assault on a Bennett and Brassard (BB84) quantum key distribution protocol is ex-perimentally showed to expose the robustness of excessive-dimensional states in quantum cryptography.

Experimental demonstration of entanglement-enabled universal quantum cloning in a circuit

No-cloning theorem forbids perfect cloning of an unknown quantum state. A universal quantum cloning machine (UQCM), capable of producing two copies of any input qubit with the optimal fidelity, is of fundamental interest and has applications in quantum information processing. This is enabled by delicately tailored nonclassical correlations between the input qubit and the copying qubits, which distinguish the UQCM from a classical counterpart, but whose experimental demonstrations are still lacking. We here implement the UQCM in a superconducting circuit and investigate these correlations. The measured entanglements well agree with our theoretical prediction that they are independent of the input state and thus constitute a universal quantum behavior of the UQCM that was not previously revealed. Another feature of our experiment is the realization of deterministic and individual cloning, in contrast to previously demonstrated UQCMs, which either were probabilistic or did not constitute true cloning of individual qubits.

Post-Quantum Cryptography and Quantum Cloning

In the last two decades, the field of post-quantum cryptography has had an overwhelming response among research communities. The ability of quantum computers to factorize large numbers could break many of well-known RSA cryptosystem and discrete log-based cryptosystem. Thus, post-quantum cryptography offers secure alternatives which are implemented on classical computers and is secure against attacks by quantum computers. The significant benefits of post-quantum cryptosystems are that they can be executed quickly and efficiently on desktops, smartphones, and the Internet of Things (IoTs) after some minor software updates. The main objective of this chapter is to give an outline of major developments in privacy protectors to reply to the forthcoming threats caused by quantum systems. In this chapter, we have presented crucial classes of cryptographic systems to resist attacks by classical and quantum computers. Furthermore, a review of different classes of quantum cloning is presented.