Juan Miguel Arrazola

Quantum fingerprinting with coherent states and a constant mean number of photons

We present a protocol for quantum fingerprinting that is ready to be implemented with current technology and is robust to experimental errors. The basis of our scheme is an implementation of the signal states in terms of a coherent state in a superposition of time-bin modes. Experimentally, this requires only the ability to prepare coherent states of low amplitude, and to interfere them in a balanced beam splitter. The states used in the protocol are arbitrarily close in trace distance to states of

Experimental quantum fingerprinting with weak coherent pulses

\mathcal{O}(\log_2 n)

Quantum Communication with Coherent States and Linear Optics

qubits, thus exhibiting an exponential separation in communication complexity compared to the classical case. The protocol uses a number of optical modes that is proportional to the size

Accessible nonlinear entanglement witnesses

n

Quantum money with nearly optimal error tolerance

of the input bit-strings, but a total mean photon number that is constant and independent of

Reliable Entanglement Verification

n

Practical quantum retrieval games

. Given the expended resources, our protocol achieves a task that is provably impossible using classical communication only. In fact, even in the presence of realistic experimental errors and loss, we show that there exist a large range of input sizes for which our quantum protocol requires communication that can be more than two orders of magnitude smaller than a classical fingerprinting protocol.

Quantum Communication Complexity with Coherent States and Linear Optics

Quantum communication holds the promise of creating disruptive technologies that will play an essential role in future communication networks. For example, the study of quantum communication complexity has shown that quantum communication allows exponential reductions in the information that must be transmitted to solve distributed computational tasks. Recently, protocols that realize this advantage using optical implementations have been proposed. Here we report a proof-of-concept experimental demonstration of a quantum fingerprinting system that is capable of transmitting less information than the best-known classical protocol. Our implementation is based on a modified version of a commercial quantum key distribution system using off-the-shelf optical components over telecom wavelengths, and is practical for messages as large as 100 Mbits, even in the presence of experimental imperfections. Our results provide a first step in the development of experimental quantum communication complexity.

Mapping Qubit Protocols to Coherent-State Protocols in Quantum Communication

that use only a sequence of coherent states, linear optics operations, and measurements with single-photon threshold detectors. The new class of protocols requires a number of optical modes equal to the dimension of the original states, but the total number of photons can be chosen independently from the dimension and is typically very small. The protocols obtained from the mapping share important properties with the original ones, meaning that they can also full the goal that the original protocols where intended to achieve. Overall, the mapping is suitable for its application to protocols that originally require a moderate number of qubits, but are still hard to implement with usual methods. In the remainder of this paper, we describe the mapping in detail and discuss the various properties of the coherent-state protocols. We proceed by examining how the mapping can be applied to construct protocols in quantum communication complexity and describe protocols for the hidden matching problem and for quantum digital signatures, both of which can be realized with technology that is within current reach.

Average iterations of accessible nonlinear witnesses

(Dated: December 21, 2013)Verification of entanglement is an important tool to characterize sources and devices for use inquantum computing and communication applications. In a vast majority of experiments entangle-ment witnesses (EW) are used in order to prove the presence of entanglement in a quantum state.EWs can be constructed from available measurement results and do not require a reconstruction ofthe whole density matrix (full tomography), which is especially valuable for high-dimensional sys-tems. We provide a method to construct