944 research outputs found
Generalized Remote Preparation of Arbitrary -qubit Entangled States via Genuine Entanglements
Herein, we present a feasible, general protocol for quantum communication
within a network via generalized remote preparation of an arbitrary -qubit
entangled state designed with genuine tripartite
Greenberger--Horne--Zeilinger-type entangled resources. During the
implementations, we construct novel collective unitary operations; these
operations are tasked with performing the necessary phase transfers during
remote state preparations. We have distilled our implementation methods into a
five-step procedure, which can be used to faithfully recover the desired state
during transfer. Compared to previous existing schemes, our methodology
features a greatly increased success probability. After the consumption of
auxiliary qubits and the performance of collective unitary operations, the
probability of successful state transfer is increased four-fold and eight-fold
for arbitrary two- and three-qubit entanglements when compared to other methods
within the literature, respectively. We conclude this paper with a discussion
of the presented scheme for state preparation, including: success
probabilities, reducibility and generalizability.Comment: 16 pages, 3 figures, 3 tables, Accepted to Entrop
High threshold distributed quantum computing with three-qubit nodes
In the distributed quantum computing paradigm, well-controlled few-qubit
`nodes' are networked together by connections which are relatively noisy and
failure prone. A practical scheme must offer high tolerance to errors while
requiring only simple (i.e. few-qubit) nodes. Here we show that relatively
modest, three-qubit nodes can support advanced purification techniques and so
offer robust scalability: the infidelity in the entanglement channel may be
permitted to approach 10% if the infidelity in local operations is of order
0.1%. Our tolerance of network noise is therefore a order of magnitude beyond
prior schemes, and our architecture remains robust even in the presence of
considerable decoherence rates (memory errors). We compare the performance with
that of schemes involving nodes of lower and higher complexity. Ion traps, and
NV- centres in diamond, are two highly relevant emerging technologies.Comment: 5 figures, 12 pages in single column format. Revision has more
detailed comparison with prior scheme
Robust concurrent remote entanglement between two superconducting qubits
Entangling two remote quantum systems which never interact directly is an
essential primitive in quantum information science and forms the basis for the
modular architecture of quantum computing. When protocols to generate these
remote entangled pairs rely on using traveling single photon states as carriers
of quantum information, they can be made robust to photon losses, unlike
schemes that rely on continuous variable states. However, efficiently detecting
single photons is challenging in the domain of superconducting quantum circuits
because of the low energy of microwave quanta. Here, we report the realization
of a robust form of concurrent remote entanglement based on a novel microwave
photon detector implemented in the superconducting circuit quantum
electrodynamics (cQED) platform of quantum information. Remote entangled pairs
with a fidelity of are generated at Hz. Our experiment
opens the way for the implementation of the modular architecture of quantum
computation with superconducting qubits.Comment: Main paper: 7 pages, 4 figures; Appendices: 14 pages, 9 figure
Loss-tolerant parity measurement for distant quantum bits
We propose a scheme to measure the parity of two distant qubits, while
ensuring that losses on the quantum channel between them does not destroy
coherences within the parity subspaces. This capability enables deterministic
preparation of highly entangled qubit states whose fidelity is not limited by
the transmission loss. The key observation is that for a probe electromagnetic
field in a particular quantum state, namely a superposition of two coherent
states of opposite phases, the transmission loss stochastically applies a
near-unitary back-action on the probe state. This leads to a parity measurement
protocol where the main effect of the transmission losses is a decrease in the
measurement strength. By repeating the non-destructive (weak) parity
measurement, one achieves a high-fidelity entanglement in spite of a
significant transmission loss
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