27 research outputs found
Quantum information with continuous variables
Quantum information is a rapidly advancing area of interdisciplinary
research. It may lead to real-world applications for communication and
computation unavailable without the exploitation of quantum properties such as
nonorthogonality or entanglement. We review the progress in quantum information
based on continuous quantum variables, with emphasis on quantum optical
implementations in terms of the quadrature amplitudes of the electromagnetic
field.Comment: accepted for publication in Reviews of Modern Physic
Tensor Networks and Quantum Error Correction
We establish several relations between quantum error correction (QEC) and
tensor network (TN) methods of quantum many-body physics. We exhibit
correspondences between well-known families of QEC codes and TNs, and
demonstrate a formal equivalence between decoding a QEC code and contracting a
TN. We build on this equivalence to propose a new family of quantum codes and
decoding algorithms that generalize and improve upon quantum polar codes and
successive cancellation decoding in a natural way.Comment: Accepted in Phys. Rev. Lett. 8 pages, 9 figure
An improved rate region for the classical-quantum broadcast channel
We present a new achievable rate region for the two-user binary-input
classical-quantum broadcast channel. The result is a generalization of the
classical Marton-Gelfand-Pinsker region and is provably larger than the best
previously known rate region for classical-quantum broadcast channels. The
proof of achievability is based on the recently introduced polar coding scheme
and its generalization to quantum network information theory.Comment: 5 pages, double column, 1 figure, based on a result presented in the
Master's thesis arXiv:1501.0373
Optical Interferometry with Quantum Networks
We propose a method for optical interferometry in telescope arrays assisted
by quantum networks. In our approach, the quantum state of incoming photons
along with an arrival time index is stored in a binary qubit code at each
receiver. Nonlocal retrieval of the quantum state via entanglement-assisted
parity checks at the expected photon arrival rate allows for direct extraction
of the phase difference, effectively circumventing transmission losses between
nodes. Compared to prior proposals, our scheme (based on efficient quantum data
compression) offers an exponential decrease in required entanglement bandwidth.
Experimental implementation is then feasible with near-term technology,
enabling optical imaging of astronomical objects akin to well-established radio
interferometers and pushing resolution beyond what is practically achievable
classically.Comment: 7 + 6 pages, 3 + 1 figures; v2 - clarifications and further
discussion of implementation; v3 - close to published versio
Magic state distillation with punctured polar codes
We present a scheme for magic state distillation using punctured polar codes.
Our results build on some recent work by Bardet et al. (ISIT, 2016) who
discovered that polar codes can be described algebraically as decreasing
monomial codes. Using this powerful framework, we construct tri-orthogonal
quantum codes (Bravyi et al., PRA, 2012) that can be used to distill magic
states for the gate. An advantage of these codes is that they permit the
use of the successive cancellation decoder whose time complexity scales as
. We supplement this with numerical simulations for the erasure
channel and dephasing channel. We obtain estimates for the dimensions and error
rates for the resulting codes for block sizes up to for the erasure
channel and for the dephasing channel. The dimension of the
triply-even codes we obtain is shown to scale like for the binary
erasure channel at noise rate and for the dephasing
channel at noise rate . The corresponding bit error rates drop to
roughly for the erasure channel and for
the dephasing channel respectively.Comment: 18 pages, 4 figure