58 research outputs found
Sound clocks and sonic relativity
Sound propagation within certain non-relativistic condensed matter models
obeys a relativistic wave equation despite such systems admitting entirely
non-relativistic descriptions. A natural question that arises upon
consideration of this is, "do devices exist that will experience the relativity
in these systems?" We describe a thought experiment in which 'acoustic
observers' possess devices called sound clocks that can be connected to form
chains. Careful investigation shows that appropriately constructed chains of
stationary and moving sound clocks are perceived by observers on the other
chain as undergoing the relativistic phenomena of length contraction and time
dilation by the Lorentz factor, with c the speed of sound. Sound clocks within
moving chains actually tick less frequently than stationary ones and must be
separated by a shorter distance than when stationary to satisfy simultaneity
conditions. Stationary sound clocks appear to be length contracted and time
dilated to moving observers due to their misunderstanding of their own state of
motion with respect to the laboratory. Observers restricted to using sound
clocks describe a universe kinematically consistent with the theory of special
relativity, despite the preferred frame of their universe in the laboratory.
Such devices show promise in further probing analogue relativity models, for
example in investigating phenomena that require careful consideration of the
proper time elapsed for observers.Comment: (v2) consistent with published version; (v1) 15 pages, 9 figure
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
Simulating quantum effects of cosmological expansion using a static ion trap
We propose a new experimental testbed that uses ions in the collective ground
state of a static trap for studying the analog of quantum-field effects in
cosmological spacetimes, including the Gibbons-Hawking effect for a single
detector in de Sitter spacetime, as well as the possibility of modeling
inflationary structure formation and the entanglement signature of de Sitter
spacetime. To date, proposals for using trapped ions in analog gravity
experiments have simulated the effect of gravity on the field modes by directly
manipulating the ions' motion. In contrast, by associating laboratory time with
conformal time in the simulated universe, we can encode the full effect of
curvature in the modulation of the laser used to couple the ions' vibrational
motion and electronic states. This model simplifies the experimental
requirements for modeling the analog of an expanding universe using trapped
ions and enlarges the validity of the ion-trap analogy to a wide range of
interesting cases.Comment: (v2) revisions based on referee comments, figure added for clarity;
(v1) 17 pages, no figure
Weaving quantum optical frequency combs into continuous-variable hypercubic cluster states
Cluster states with higher-dimensional lattices that cannot be physically
embedded in three-dimensional space have important theoretical interest in
quantum computation and quantum simulation of topologically ordered
condensed-matter systems. We present a simple, scalable, top-down method of
entangling the quantum optical frequency comb into hypercubic-lattice
continuous-variable cluster states of a size of about 10^4 quantum field modes,
using existing technology. A hypercubic lattice of dimension D (linear, square,
cubic, hypercubic, etc.) requires but D optical parametric oscillators with
bichromatic pumps whose frequency splittings alone determine the lattice
dimensionality and the number of copies of the state.Comment: 8 pages, 5 figures, submitted for publicatio
An efficient, concatenated, bosonic code for additive Gaussian noise
Bosonic codes offer noise resilience for quantum information processing. A
common type of noise in this setting is additive Gaussian noise, and a
long-standing open problem is to design a concatenated code that achieves the
hashing bound for this noise channel. Here we achieve this goal using a
Gottesman-Kitaev-Preskill (GKP) code to detect and discard error-prone qubits,
concatenated with a quantum parity code to handle the residual errors. Our
method employs a linear-time decoder and has applications in a wide range of
quantum computation and communication scenarios.Comment: 7 pages, 3 figure
Noise analysis of single-qumode Gaussian operations using continuous-variable cluster states
We consider measurement-based quantum computation that uses scalable
continuous-variable cluster states with a one-dimensional topology. The
physical resource, known here as the dual-rail quantum wire, can be generated
using temporally multiplexed offline squeezing and linear optics or by using a
single optical parametric oscillator. We focus on an important class of quantum
gates, specifically Gaussian unitaries that act on single modes, which gives
universal quantum computation when supplemented with multi-mode operations and
photon-counting measurements. The dual-rail wire supports two routes for
applying single-qumode Gaussian unitaries: the first is to use traditional
one-dimensional quantum-wire cluster-state measurement protocols. The second
takes advantage of the dual-rail quantum wire in order to apply unitaries by
measuring pairs of qumodes called macronodes. We analyze and compare these
methods in terms of the suitability for implementing single-qumode Gaussian
measurement-based quantum computation.Comment: 25 pages, 9 figures, more accessible to general audienc
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