Demonstration of Blind Quantum Computing

Barz, Stefanie
Kashefi, Elham
Broadbent, Anne
Fitzsimons, Joseph F.
Zeilinger, Anton
Walther, Philip

¹Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria. ²Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, A-1090 Vienna, Austria. ³School of Informatics, University of Edinburgh, 10 Crichton Street, Edinburgh EH8 9AB, UK. ⁴Institute for Quantum Computing, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada, ⁵Department of Combinatorics and Optimization, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada. ⁶Centre for Quantum Technologies, National University of Singapore, Block S15, 3 Science Drive 2, 117543 Singapore. ⁷School of Physics, University College Dublin, Belfield, Dublin 4, Ireland.
^*To whom correspondence should be addressed. E-mail: [email protected]

Science 335(6066):p 303-308, January 20, 2012.

Quantum computers, besides offering substantial computational speedups, are also expected to preserve the privacy of a computation. We present an experimental demonstration of blind quantum computing in which the input, computation, and output all remain unknown to the computer. We exploit the conceptual framework of measurement-based quantum computation that enables a client to delegate a computation to a quantum server. Various blind delegated computations, including one- and two-qubit gates and the Deutsch and Grover quantum algorithms, are demonstrated. The client only needs to be able to prepare and transmit individual photonic qubits. Our demonstration is crucial for unconditionally secure quantum cloud computing and might become a key ingredient for real-life applications, especially when considering the challenges of making powerful quantum computers widely available.