157 research outputs found
Generalized self-testing and the security of the 6-state protocol
Self-tested quantum information processing provides a means for doing useful
information processing with untrusted quantum apparatus. Previous work was
limited to performing computations and protocols in real Hilbert spaces, which
is not a serious obstacle if one is only interested in final measurement
statistics being correct (for example, getting the correct factors of a large
number after running Shor's factoring algorithm). This limitation was shown by
McKague et al. to be fundamental, since there is no way to experimentally
distinguish any quantum experiment from a special simulation using states and
operators with only real coefficients.
In this paper, we show that one can still do a meaningful self-test of
quantum apparatus with complex amplitudes. In particular, we define a family of
simulations of quantum experiments, based on complex conjugation, with two
interesting properties. First, we are able to define a self-test which may be
passed only by states and operators that are equivalent to simulations within
the family. This extends work of Mayers and Yao and Magniez et al. in
self-testing of quantum apparatus, and includes a complex measurement. Second,
any of the simulations in the family may be used to implement a secure 6-state
QKD protocol, which was previously not known to be implementable in a
self-tested framework.Comment: To appear in proceedings of TQC 201
Quantum information cannot be split into complementary parts
We prove a new impossibility for quantum information (the no-splitting
theorem): an unknown quantum bit (qubit) cannot be split into two complementary
qubits. This impossibility, together with the no-cloning theorem, demonstrates
that an unknown qubit state is a single entity, which cannot be cloned or
split. This sheds new light on quantum computation and quantum information.Comment: 9 pages, 1 figur
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
Device-independent dimension test in a multiparty Bell experiment
A device-independent dimension test for a Bell experiment aims to estimate
the underlying Hilbert space dimension that is required to produce given
measurement statistical data without any other assumptions concerning the
quantum apparatus. Previous work mostly deals with the two-party version of
this problem. In this paper, we propose a very general and robust approach to
test the dimension of any subsystem in a multiparty Bell experiment. Our
dimension test stems from the study of a new multiparty scenario which we call
prepare-and-distribute. This is like the prepare-and-measure scenario, but the
quantum state is sent to multiple, non-communicating parties. Through specific
examples, we show that our test results can be tight. Furthermore, we compare
the performance of our test to results based on known bipartite tests, and
witness remarkable advantage, which indicates that our test is of a true
multiparty nature. We conclude by pointing out that with some partial
information about the quantum states involved in the experiment, it is possible
to learn other interesting properties beyond dimension.Comment: 10 pages, 2 figure
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