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 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.”
SOURCE – University of Vienna
