462 research outputs found
Self-testing graph states
We give a construction for a self-test for any connected graph state. In
other words, for each connected graph state we give a set of non-local
correlations that can only be achieved (quantumly) by that particular graph
state and certain local measurements. The number of correlations considered is
small, being linear in the number of vertices in the graph. We also prove
robustness for the test.Comment: 21 page
Self-testing in parallel
Self-testing allows us to determine, through classical interaction only,
whether some players in a non-local game share particular quantum states. Most
work on self-testing has concentrated on developing tests for small states like
one pair of maximally entangled qubits, or on tests where there is a separate
player for each qubit, as in a graph state. Here we consider the case of
testing many maximally entangled pairs of qubits shared between two players.
Previously such a test was shown where testing is sequential, i.e., one pair is
tested at a time. Here we consider the parallel case where all pairs are tested
simultaneously, giving considerably more power to dishonest players. We derive
sufficient conditions for a self-test for many maximally entangled pairs of
qubits shared between two players and also two constructions for self-tests
where all pairs are tested simultaneously.Comment: 22 page
Insider-proof encryption with applications for quantum key distribution
It has been pointed out that current protocols for device independent quantum
key distribution can leak key to the adversary when devices are used repeatedly
and that this issue has not been addressed. We introduce the notion of an
insider-proof channel. This allows us to propose a means by which devices with
memories could be reused from one run of a device independent quantum key
distribution protocol to the next while bounding the leakage to Eve, under the
assumption that one run of the protocol could be completed securely using
devices with memories.Comment: 20 pages, version 2: new presentation introducing the insider-proof
channel as a cryptographic elemen
On the power quantum computation over real Hilbert spaces
We consider the power of various quantum complexity classes with the
restriction that states and operators are defined over a real, rather than
complex, Hilbert space. It is well know that a quantum circuit over the complex
numbers can be transformed into a quantum circuit over the real numbers with
the addition of a single qubit. This implies that BQP retains its power when
restricted to using states and operations over the reals. We show that the same
is true for QMA(k), QIP(k), QMIP, and QSZK.Comment: Significant improvements from previous version, in particular showing
both containments (eg. QMA_R is in QMA and vice versa
Purple Kites
In lieu of an abstract, below is the essay\u27s first paragraph.
I often recall my kite-days. Whenever the city streets seem to fill up suddenly with wintry people, whenever my business takes me through hustling, friendless sections of town, I let my mind wander back. Whenever I begin to look into every face, I see with suspicion. Whenever I find myself categorizing everybody into neat pidgen-holes, labelling this one a competitor, that one a sucker, the other an out-and-out enemy, then I know it is time to go back to the deserted playground with Runner (we called him Runner then because his nose was always running), time to pretend that both of us are just now running through the high dried grass, looking up at our purple kites trailing behind us
Simulating quantum systems using real Hilbert spaces
We develop a means of simulating the evolution and measurement of a
multipartite quantum state under discrete or continuous evolution using another
quantum system with states and operators lying in a real Hilbert space. This
extends previous results which were unable to simulate local evolution and
measurements with local operators and was limited to discrete evolution. We
also detail applications to Bell inequalities and self-testing of quantum
apparatus.Comment: 4 page
Interactive proofs for BQP via self-tested graph states
Using the measurement-based quantum computation model, we construct
interactive proofs with non-communicating quantum provers and a classical
verifier. Our construction gives interactive proofs for all languages in BQP
with a polynomial number of quantum provers, each of which, in the honest case,
performs only a single measurement.
Our techniques use self-tested graph states. In this regard we introduce two
important improvements over previous work. Specifically, we derive new error
bounds which scale polynomially with the size of the graph compared with
exponential dependence on the size of the graph in previous work. We also
extend the self-testing error bounds on measurements to a very general set
which includes the adaptive measurements used for measurement-based quantum
computation as a special case.Comment: 53 page
The Coming-Out Party
In lieu of an abstract, below is the essay\u27s first paragraph.
Note: Although we do not have the space to print the whole of this play, we the editors thought that the readers of the Angle would be interested in sampling a few selections from it
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