Speaker: Jonathan C. F. Matthews
Session: Quantum sensors
See program for placement.
Entangled Multi-Photon States in Waveguide for Quantum Metrology
J C F Matthews1, A Politi1, D Bonneau1, and J L O’Brien1
Centre for Quantum Photonics, H. H. Wills Physics Laboratory & Department of Electrical and Electronic
Engineering, University of Bristol, UK
Multi-photon quantum metrology aims to increase precision of measuring phase Δϕ using large superposition
states of photons, entangled in number and one other optical degree of freedom (typically path or polarization).
So-called “NOON” states are typical examples capable of Heisenberg limited (Δϕ~1/N) “super-sensitive”
precision, beyond the classical shot noise limit Δϕ~1/√N .
Defined with N photons entangled across modes a and b, N :: 0 = N ( a
0 b + e iNφ 0 a
N b )/ 2 , NOON
states have been experimentally demonstrated, observing increased resolution in sensitivity of optical phase φ
using large scale bulk optical circuitry. Here we explore the implementation of integrated waveguide circuits as
an avenue for practical quantum metrology, exploiting key benefits such as miniaturised circuitry and inherent
interferometer stability. €
Figure 1 Examples of waveguide chips used for integrated quantum metrology investigation. (A) Mach Zehnder
inteferometer consisting of evanescent couplers used as 50:50 beam splitters, for observing post-selected two- and four-
photon super resolution fringes. (B) Cross section the Silica-on-Silicon waveguide architecture used, featuring a resistive
heating element (R) placed above one waveguide to control optical phase. (C) Simulation of the single mode at 780nm in
the architecture. (D) Schematic of the linear optical circuit used to herald 2- and 4-photon NOON states.
We present the manipulation of NOON states within integrated waveguide circuits . We also report results for
a four- and six-photon heralding scheme for NOON state generation . Using only linear optics and projective
measurements, we experimentally analyse the scheme for heralding two- and four-photon NOON states as well
as an entangled four photon state more robust to balanced loss . With these results, we highlight the potential
application of integrated linear optical circuitry for practical of quantum metrology that will use either NOON
states or similar number entangled states more robust to loss.
 V. Giovannetti, S. Lloyd, L. Maccone, Science 306, 1330 (2004),
 J. C. F. Matthews, A. Politi, A. Stefanov, J. L. O’Brien, Nature Photonics. 3 346 (2009).
 H. Lee, P. Kok, N. J. Cerf, J. P. Dowling Phys. Rev. A 65 030101 (2002).
 J. C. F. Matthews, A. Politi, D. Bonneau, J. L. O’Brien arXiv:1005.5119 (2010).
PQE-2011 Abstract Processed 29 November 2010 0