1,371 research outputs found
Device-independent verifiable blind quantum computation
As progress on experimental quantum processors continues to advance, the problem of verifying the correct operation of such devices is becoming a pressing concern. The recent discovery of protocols for verifying computation performed by entangled but non-communicating quantum processors holds the promise of certifying the correctness of arbitrary quantum computations in a fully device-independent manner. Unfortunately, all known schemes have prohibitive overhead, with resources scaling as extremely high degree polynomials in the number of gates constituting the computation. Here we present a novel approach based on a combination of verified blind quantum computation and Bell state self-testing. This approach has dramatically reduced overhead, with resources scaling as only O(m4lnm) in the number of gates
Parallel remote state preparation for fully device-independent verifiable blind quantum computation
We introduce a device-independent two-prover scheme in which a classical
verifier is able to use a simple untrusted quantum measurement device (the
client device) to securely delegate a quantum computation to an untrusted
quantum server. To do this, we construct a parallel self-testing protocol to
perform device-independent remote state preparation of qubits and compose
this with the unconditionally secure universal verifiable blind quantum
computation (VBQC) scheme of J. F. Fitzsimons and E. Kashefi [Phys. Rev. A 96,
012303 (2017)]. Our self-test achieves a multitude of desirable properties for
the application we consider, giving rise to practical and fully
device-independent VBQC. It certifies parallel measurements of all cardinal and
intercardinal directions in the -plane as well as the computational basis,
uses few input questions (of size logarithmic in for the client and a
constant number communicated to the server), and requires only single-qubit
measurements to be performed by the client device.Comment: 55 pages, 3 figure
Flow Ambiguity: A Path Towards Classically Driven Blind Quantum Computation
Blind quantum computation protocols allow a user to delegate a computation to
a remote quantum computer in such a way that the privacy of their computation
is preserved, even from the device implementing the computation. To date, such
protocols are only known for settings involving at least two quantum devices:
either a user with some quantum capabilities and a remote quantum server or two
or more entangled but noncommunicating servers. In this work, we take the first
step towards the construction of a blind quantum computing protocol with a
completely classical client and single quantum server. Specifically, we show
how a classical client can exploit the ambiguity in the flow of information in
measurement-based quantum computing to construct a protocol for hiding critical
aspects of a computation delegated to a remote quantum computer. This ambiguity
arises due to the fact that, for a fixed graph, there exist multiple choices of
the input and output vertex sets that result in deterministic measurement
patterns consistent with the same fixed total ordering of vertices. This allows
a classical user, computing only measurement angles, to drive a
measurement-based computation performed on a remote device while hiding
critical aspects of the computation.Comment: (v3) 14 pages, 6 figures. expands introduction and definition of
flow, corrects typos to increase readability; contains a new figure to
illustrate example run of CDBQC protocol; minor changes to match the
published version.(v2) 12 pages, 5 figures. Corrects motivation for
quantities used in blindness analysi
Unconditionally verifiable blind computation
Blind Quantum Computing (BQC) allows a client to have a server carry out a
quantum computation for them such that the client's input, output and
computation remain private. A desirable property for any BQC protocol is
verification, whereby the client can verify with high probability whether the
server has followed the instructions of the protocol, or if there has been some
deviation resulting in a corrupted output state. A verifiable BQC protocol can
be viewed as an interactive proof system leading to consequences for complexity
theory. The authors, together with Broadbent, previously proposed a universal
and unconditionally secure BQC scheme where the client only needs to be able to
prepare single qubits in separable states randomly chosen from a finite set and
send them to the server, who has the balance of the required quantum
computational resources. In this paper we extend that protocol with new
functionality allowing blind computational basis measurements, which we use to
construct a new verifiable BQC protocol based on a new class of resource
states. We rigorously prove that the probability of failing to detect an
incorrect output is exponentially small in a security parameter, while resource
overhead remains polynomial in this parameter. The new resource state allows
entangling gates to be performed between arbitrary pairs of logical qubits with
only constant overhead. This is a significant improvement on the original
scheme, which required that all computations to be performed must first be put
into a nearest neighbour form, incurring linear overhead in the number of
qubits. Such an improvement has important consequences for efficiency and
fault-tolerance thresholds.Comment: 46 pages, 10 figures. Additional protocol added which allows
arbitrary circuits to be verified with polynomial securit
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