Photonic Quantum Computing

Abstract:
Quantum physics has revolutionized our understanding of

information processing and enables computational speed-ups that are

unattainable using classical computers. In this talk I will present a

series of experiments in the field of photonic quantum computing. The

first experiment is in the field of photonic state engineering and

realizes the generation of heralded polarization-entangled photon

pairs [1]. It overcomes the limited applicability of photon-based

schemes for quantum information processing tasks, which arises from

the probabilistic nature of photon generation. The second experiment

uses polarization-entangled photonic qubits to implement blind

quantum computing, a new concept in quantum computing [2, 3]. Blind

quantum computing enables a nearly-classical client to access the

resources of a more computationally-powerful quantum server without

divulging the content of the requested computation. A third

experiment shows how the concept of blind quantum computing can be

applied to the field of verification. A new method is developed and

experimentally demonstrated to verify the correctness and the

entangling capabilities of a quantum computer [4]. Finally, I will

present an experiment realizing a measured universal two-qubit

photonic quantum processor by applying two consecutive CNOT gates to

the same pair of polarization-encoded qubits. To demonstrate the

flexibility of our system, we implement various instances of the

quantum algorithm for the solving of systems of linear equations [5].

[1] S. Barz, G. Cronenberg, A. Zeilinger, and P. Walther, Nature

Photonics 4, 553 (2010)

[2] A. Broadbent, J. Fitzsimons and E. Kashefi, in Proceedings of the

50th Annual Symposium on Foundations of Computer Science, 517 (2009)

[3] S. Barz, E. Kashefi, A. Broadbent, J. Fitzsimons, A. Zeilinger,

and P. Walther, Science 335, 303 (2012)

[4] S. Barz, J. Fitzsimons, E. Kashefi, and P. Walther, Nature

Physics, AOP, DOI: 10.1038/nphys2763 (2013)

[5] S. Barz, I. Kassal, M. Ringbauer, Y. O. Lipp, B. Dakic, A.

Aspuru-Guzik, P. Walther, arXiv:1302.1210