1,023 research outputs found
Benchmarking projective simulation in navigation problems
Projective simulation (PS) is a model for intelligent agents with a
deliberation capacity that is based on episodic memory. The model has been
shown to provide a flexible framework for constructing reinforcement-learning
agents, and it allows for quantum mechanical generalization, which leads to a
speed-up in deliberation time. PS agents have been applied successfully in the
context of complex skill learning in robotics, and in the design of
state-of-the-art quantum experiments. In this paper, we study the performance
of projective simulation in two benchmarking problems in navigation, namely the
grid world and the mountain car problem. The performance of PS is compared to
standard tabular reinforcement learning approaches, Q-learning and SARSA. Our
comparison demonstrates that the performance of PS and standard learning
approaches are qualitatively and quantitatively similar, while it is much
easier to choose optimal model parameters in case of projective simulation,
with a reduced computational effort of one to two orders of magnitude. Our
results show that the projective simulation model stands out for its simplicity
in terms of the number of model parameters, which makes it simple to set up the
learning agent in unknown task environments.Comment: 8 pages, 10 figure
Teleporting bipartite entanglement using maximally entangled mixed channels
The ability to teleport entanglement through maximally entangled mixed states
as defined by concurrence and linear entropy is studied. We show how the
teleported entanglement depends on the quality of the quantum channel used, as
defined through its entanglement and mixedness, as well as the form of the
target state to be teleported. We present new results based on the fidelity of
the teleported state as well as an experimental set-up that is immediately
implementable with currently available technology.Comment: 8 pages, 7 figures, RevTeX4, Accepted for publication in the IJQI
special issue on Distributed Quantum Information Processin
Projective simulation with generalization
The ability to generalize is an important feature of any intelligent agent.
Not only because it may allow the agent to cope with large amounts of data, but
also because in some environments, an agent with no generalization capabilities
cannot learn. In this work we outline several criteria for generalization, and
present a dynamic and autonomous machinery that enables projective simulation
agents to meaningfully generalize. Projective simulation, a novel, physical
approach to artificial intelligence, was recently shown to perform well in
standard reinforcement learning problems, with applications in advanced
robotics as well as quantum experiments. Both the basic projective simulation
model and the presented generalization machinery are based on very simple
principles. This allows us to provide a full analytical analysis of the agent's
performance and to illustrate the benefit the agent gains by generalizing.
Specifically, we show that already in basic (but extreme) environments,
learning without generalization may be impossible, and demonstrate how the
presented generalization machinery enables the projective simulation agent to
learn.Comment: 14 pages, 9 figure
Simple proof of confidentiality for private quantum channels in noisy environments
Complete security proofs for quantum communication protocols can be
notoriously involved, which convolutes their verification, and obfuscates the
key physical insights the security finally relies on. In such cases, for the
majority of the community, the utility of such proofs may be restricted. Here
we provide a simple proof of confidentiality for parallel quantum channels
established via entanglement distillation based on hashing, in the presence of
noise, and a malicious eavesdropper who is restricted only by the laws of
quantum mechanics. The direct contribution lies in improving the linear
confidentiality levels of recurrence-type entanglement distillation protocols
to exponential levels for hashing protocols. The proof directly exploits the
security relevant physical properties: measurement-based quantum computation
with resource states and the separation of Bell-pairs from an eavesdropper. The
proof also holds for situations where Eve has full control over the input
states, and obtains all information about the operations and noise applied by
the parties. The resulting state after hashing is private, i.e., disentangled
from the eavesdropper. Moreover, the noise regimes for entanglement
distillation and confidentiality do not coincide: Confidentiality can be
guaranteed even in situation where entanglement distillation fails. We extend
our results to multiparty situations which are of special interest for secure
quantum networks.Comment: 5 + 11 pages, 0 + 4 figures, A. Pirker and M. Zwerger contributed
equally to this work, replaced with accepted versio
Long-range big quantum-data transmission
We introduce an alternative type of quantum repeater for long-range quantum
communication with improved scaling with the distance. We show that by
employing hashing, a deterministic entanglement distillation protocol with
one-way communication, one obtains a scalable scheme that allows one to reach
arbitrary distances, with constant overhead in resources per repeater station,
and ultrahigh rates. In practical terms, we show that also with moderate
resources of a few hundred qubits at each repeater station, one can reach
intercontinental distances. At the same time, a measurement-based
implementation allows one to tolerate high loss, but also operational and
memory errors of the order of several percent per qubit. This opens the way for
long-distance communication of big quantum data.Comment: revised manuscript including new result
Quantum processing photonic states in optical lattices
The mapping of photonic states to collective excitations of atomic ensembles
is a powerful tool which finds a useful application in the realization of
quantum memories and quantum repeaters. In this work we show that cold atoms in
optical lattices can be used to perform an entangling unitary operation on the
transferred atomic excitations. After the release of the quantum atomic state,
our protocol results in a deterministic two qubit gate for photons. The
proposed scheme is feasible with current experimental techniques and robust
against the dominant sources of noise.Comment: 4 pages, 4 figure
- …