Related papers: Knowledge-Concealing Evidencing of Knowledge about…
Secure communication protocols are becoming increasingly important, e.g. for internet-based communication. Quantum key distribution allows two parties, commonly called Alice and Bob, to generate a secret sequence of 0s and 1s called a key…
There had been well known claims of ``provably unbreakable'' quantum protocols for bit commitment and coin tossing. However, we, and independently Mayers, showed that all proposed quantum bit commitment (and therefore coin tossing) schemes…
Quantum physics exhibits remarkable distinguishing characteristics. For example, it gives only probabilistic predictions (non-determinism) and does not allow copying of unknown state (no-cloning). Quantum correlations may be stronger than…
The security of two-state quantum key distribution against individual attack is estimated when the channel has losses and noises. We assume that Alice and Bob use two nonorthogonal single-photon polarization states. To make our analysis…
Employing the fundamental laws of quantum physics, Quantum Key Distribution (QKD) promises the unconditionally secure distribution of cryptographic keys. However, in practical realisations, a QKD protocol is only secure, when the quantum…
We present the first protocol for the anonymous transmission of a quantum state that is information-theoretically secure against an active adversary, without any assumption on the number of corrupt participants. The anonymity of the sender…
The `no communication' theorem prohibits superluminal communication by showing that any measurement by Alice on an entangled system cannot change the reduced density matrix of Bob's state, and hence the expectation value of any measurement…
It is demonstrated that for the entanglement-based version of the Bennett-Brassard (BB84) quantum key distribution protocol, Alice and Bob share provable entanglement if and only if the estimated qubit error rate is below 25% or above 75%.…
Blind quantum computation (BQC) is a new type of quantum computation model. BQC allows a client (Alice) who does not have enough sophisticated technology and knowledge to perform universal quantum computation and resorts a remote quantum…
We introduce a relativistic version of quantum encryption protocol by considering two inertial observers who wish to securely transmit quantum information encoded in a free scalar quantum field state forming Minkowski particles. In a…
In this Ph.D. thesis, I investigate the communication abilities of non-inertial observers and the precision to which they can measure parametrized states. I introduce relativistic quantum field theory with field quantisation, and the…
Several protocols for controlled teleportation were suggested by Yang, Chu, and Han [PRA 70, 022329 (2004)]. In these protocols, Alice teleports qubits (in an unknown state) to Bob iff a controller allows it. We view this problem in the…
Information about an unknown quantum state can be encoded in weak values of projectors belonging to a complete eigenbasis. We present a protocol that enables one party -- Bob -- to remotely determine the weak values corresponding to weak…
We present a quantum communication protocol which keeps all the properties of the ping-pong protocol [Phys. Rev. Lett. 89, 187902 (2002)] but improves the capacity doubly as the ping-pong protocol. Alice and Bob can use the variable…
There had been well known claims of unconditionally secure quantum protocols for bit commitment. However, we, and independently Mayers, showed that all proposed quantum bit commitment schemes are, in principle, insecure because the sender,…
In the direct communication quantum channels the authorized recipient (Bob) and the non-authorized recipient (Eve) have different abilities for verification of received information. Bob can apply the feedback to commit the sender (Alice) to…
We define the notion of a proof of knowledge in the setting where the verifier is classical, but the prover is quantum, and where the witness that the prover holds is in general a quantum state. We establish simple properties of our…
Although it is impossible for a bit commitment protocol to be both arbitrarily concealing and arbitrarily binding, it is possible for it to be both partially concealing and partially binding. This means that Bob cannot, prior to the…
Inspired from quantum key distribution, we consider wireless communication between Alice and Bob when the intermediate space between Alice and Bob is controlled by Eve. That is, our model divides the channel noise into two parts, the noise…
In the realistic quantum key distribution (QKD), Alice and Bob respectively get a quantum state from an unknown channel, whose dimension may be unknown. However, while discussing the security, sometime we need to know exact dimension, since…