254 research outputs found
Scalable boson-sampling with time-bin encoding using a loop-based architecture
We present an architecture for arbitrarily scalable boson-sampling using two
nested fiber loops. The architecture has fixed experimental complexity,
irrespective of the size of the desired interferometer, whose scale is limited
only by fiber and switch loss rates. The architecture employs time-bin
encoding, whereby the incident photons form a pulse train, which enters the
loops. Dynamically controlled loop coupling ratios allow the construction of
the arbitrary linear optics interferometers required for boson-sampling. The
architecture employs only a single point of interference and may thus be easier
to stabilize than other approaches. The scheme has polynomial complexity and
could be realized using demonstrated present-day technologies.Comment: 7 pages, 7 figure
Generation of Universal Linear Optics by Any Beamsplitter
In 1994, Reck et al. showed how to realize any unitary transformation on a
single photon using a product of beamsplitters and phaseshifters. Here we show
that any single beamsplitter that nontrivially mixes two modes, also densely
generates the set of unitary transformations (or orthogonal transformations, in
the real case) on the single-photon subspace with m>=3 modes. (We prove the
same result for any two-mode real optical gate, and for any two-mode optical
gate combined with a generic phaseshifter.) Experimentally, this means that one
does not need tunable beamsplitters or phaseshifters for universality: any
nontrivial beamsplitter is universal for linear optics. Theoretically, it means
that one cannot produce "intermediate" models of linear optical computation
(analogous to the Clifford group for qubits) by restricting the allowed
beamsplitters and phaseshifters: there is a dichotomy; one either gets a
trivial set or else a universal set. No similar classification theorem for
gates acting on qubits is currently known. We leave open the problem of
classifying optical gates that act on three or more modes.Comment: 14 pages; edited Lemma 3.3 and updated references. Results are
unchange
Flexible quantum circuits using scalable continuous-variable cluster states
We show that measurement-based quantum computation on scalable
continuous-variable (CV) cluster states admits more quantum-circuit flexibility
and compactness than similar protocols for standard square-lattice CV cluster
states. This advantage is a direct result of the macronode structure of these
states---that is, a lattice structure in which each graph node actually
consists of several physical modes. These extra modes provide additional
measurement degrees of freedom at each graph location, which can be used to
manipulate the flow and processing of quantum information more robustly and
with additional flexibility that is not available on an ordinary lattice.Comment: (v2) consistent with published version; (v1) 11 pages (9 figures
Universal quantum computation with the Orbital Angular Momentum of a single photon
We prove that a single photon with quantum data encoded in its orbital
angular momentum can be manipulated with simple optical elements to provide any
desired quantum computation. We will show how to build any quantum unitary
operator using beamsplitters, phase shifters, holograms and an extraction gate
based on quantum interrogation. The advantages and challenges of these approach
are then discussed, in particular the problem of the readout of the results.Comment: First version. Comments welcom
Temporal-mode continuous-variable cluster states using linear optics
I present an extensible experimental design for optical continuous-variable
cluster states of arbitrary size using four offline (vacuum) squeezers and six
beamsplitters. This method has all the advantages of a temporal-mode encoding
[Phys. Rev. Lett. 104, 250503], including finite requirements for coherence and
stability even as the computation length increases indefinitely, with none of
the difficulty of inline squeezing. The extensibility stems from a construction
based on Gaussian projected entangled pair states (GPEPS). The potential for
use of this design within a fully fault tolerant model is discussed.Comment: 9 pages, 19 color figure
One-way quantum computing with arbitrarily large time-frequency continuous-variable cluster states from a single optical parametric oscillator
One-way quantum computing is experimentally appealing because it requires
only local measurements on an entangled resource called a cluster state.
Record-size, but non-universal, continuous-variable cluster states were
recently demonstrated separately in the time and frequency domains. We propose
to combine these approaches into a scalable architecture in which a single
optical parametric oscillator and simple interferometer entangle up to
( frequencies) (unlimited number of temporal modes) into
a new and computationally universal continuous-variable cluster state. We
introduce a generalized measurement protocol to enable improved computational
performance on this new entanglement resource.Comment: (v4) Consistent with published version; (v3) Fixed typo in arXiv
abstract, 14 pages, 8 figures; (v2) Supplemental material incorporated into
main text, additional explanations added, results unchanged, 14 pages, 8
figures; (v1) 5 pages (3 figures) + 6 pages (5 figures) of supplemental
material; submitted for publicatio
Universal quantum computation with temporal-mode bilayer square lattices
We propose an experimental design for universal continuous-variable quantum
computation that incorporates recent innovations in linear-optics-based
continuous-variable cluster state generation and cubic-phase gate
teleportation. The first ingredient is a protocol for generating the
bilayer-square-lattice cluster state (a universal resource state) with temporal
modes of light. With this state, measurement-based implementation of Gaussian
unitary gates requires only homodyne detection. Second, we describe a
measurement device that implements an adaptive cubic-phase gate, up to a random
phase-space displacement. It requires a two-step sequence of homodyne
measurements and consumes a (non-Gaussian) cubic-phase state.Comment: (v2) 14 pages, 5 figures, consistent with published version; (v1) 13
pages, 5 figure
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