Via eurekalert
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Researchers have succeeded in combining the power of quantum
computing with the security of quantum cryptography and have shown that
perfectly secure cloud computing can be achieved using the principles of
quantum mechanics. They have performed an experimental demonstration of
quantum computation in which the input, the data processing, and the
output remain unknown to the quantum computer. The international team of
scientists will publish the results of the experiment, carried out at
the Vienna Center for Quantum Science and Technology (VCQ) at the
University of Vienna and the Institute for Quantum Optics and Quantum
Information (IQOQI), in the forthcoming issue of Science.
Quantum computers are expected to play an important role in future
information processing since they can outperform classical computers at
many tasks. Considering the challenges inherent in building quantum
devices, it is conceivable that future quantum computing capabilities
will exist only in a few specialized facilities around the world – much
like today's supercomputers. Users would then interact with those
specialized facilities in order to outsource their quantum computations.
The scenario follows the current trend of cloud computing: central
remote servers are used to store and process data – everything is done
in the "cloud." The obvious challenge is to make globalized computing
safe and ensure that users' data stays private.
The latest research, to appear in Science, reveals that
quantum computers can provide an answer to that challenge. "Quantum
physics solves one of the key challenges in distributed computing. It
can preserve data privacy when users interact with remote computing
centers," says Stefanie Barz, lead author of the study. This newly
established fundamental advantage of quantum computers enables the
delegation of a quantum computation from a user who does not hold any
quantum computational power to a quantum server, while guaranteeing that
the user's data remain perfectly private. The quantum server performs
calculations, but has no means to find out what it is doing – a
functionality not known to be achievable in the classical world.
The scientists in the Vienna research group have demonstrated the
concept of "blind quantum computing" in an experiment: they performed
the first known quantum computation during which the user's data stayed
perfectly encrypted. The experimental demonstration uses photons, or
"light particles" to encode the data. Photonic systems are well-suited
to the task because quantum computation operations can be performed on
them, and they can be transmitted over long distances.
The process works in the following manner. The user prepares qubits –
the fundamental units of quantum computers – in a state known only to
himself and sends these qubits to the quantum computer. The quantum
computer entangles the qubits according to a standard scheme. The actual
computation is measurement-based: the processing of quantum information
is implemented by simple measurements on qubits. The user tailors
measurement instructions to the particular state of each qubit and sends
them to the quantum server. Finally, the results of the computation are
sent back to the user who can interpret and utilize the results of the
computation. Even if the quantum computer or an eavesdropper tries to
read the qubits, they gain no useful information, without knowing the
initial state; they are "blind."
The research at the Vienna Center for
Quantum Science and Technology (VCQ) at the University of Vienna and at
the Institute for Quantum Optics and Quantum Information (IQOQI) of the
Austrian Academy of Sciences was undertaken in collaboration with the
scientists who originally invented the protocol, based at the University
of Edinburgh, the Institute for Quantum Computing (University of
Waterloo), the Centre for Quantum Technologies (National University of
Singapore), and University College Dublin.
Publication: "Demonstration of Blind Quantum Computing"
Stefanie Barz, Elham Kashefi, Anne Broadbent, Joseph Fitzsimons, Anton Zeilinger, Philip Walther.
DOI: 10.1126/science.1214707
