51 research outputs found
Universal blind quantum computation
We present a protocol which allows a client to have a server carry out a
quantum computation for her such that the client's inputs, outputs and
computation remain perfectly private, and where she does not require any
quantum computational power or memory. The client only needs to be able to
prepare single qubits randomly chosen from a finite set and send them to the
server, who has the balance of the required quantum computational resources.
Our protocol is interactive: after the initial preparation of quantum states,
the client and server use two-way classical communication which enables the
client to drive the computation, giving single-qubit measurement instructions
to the server, depending on previous measurement outcomes. Our protocol works
for inputs and outputs that are either classical or quantum. We give an
authentication protocol that allows the client to detect an interfering server;
our scheme can also be made fault-tolerant.
We also generalize our result to the setting of a purely classical client who
communicates classically with two non-communicating entangled servers, in order
to perform a blind quantum computation. By incorporating the authentication
protocol, we show that any problem in BQP has an entangled two-prover
interactive proof with a purely classical verifier.
Our protocol is the first universal scheme which detects a cheating server,
as well as the first protocol which does not require any quantum computation
whatsoever on the client's side. The novelty of our approach is in using the
unique features of measurement-based quantum computing which allows us to
clearly distinguish between the quantum and classical aspects of a quantum
computation.Comment: 20 pages, 7 figures. This version contains detailed proofs of
authentication and fault tolerance. It also contains protocols for quantum
inputs and outputs and appendices not available in the published versio
Blind topological measurement-based quantum computation
Blind quantum computation is a novel secure quantum-computing protocol that
enables Alice, who does not have sufficient quantum technology at her disposal,
to delegate her quantum computation to Bob, who has a fully fledged quantum
computer, in such a way that Bob cannot learn anything about Alice's input,
output and algorithm. A recent proof-of-principle experiment demonstrating
blind quantum computation in an optical system has raised new challenges
regarding the scalability of blind quantum computation in realistic noisy
conditions. Here we show that fault-tolerant blind quantum computation is
possible in a topologically protected manner using the
Raussendorf-Harrington-Goyal scheme. The error threshold of our scheme is
0.0043, which is comparable to that (0.0075) of non-blind topological quantum
computation. As the error per gate of the order 0.001 was already achieved in
some experimental systems, our result implies that secure cloud quantum
computation is within reach.Comment: 17 pages, 5 figure
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