1. Strathclyde Optics Division
Overview by
Erling Riis

2. Strathclyde Optics Division
Computational Nonlinear & Quantum Optics Group
BECs and Cold Atoms
Computational Nonlinear Optics
Future Light Sources
Nanophotonics
Nonlinear Photonics
Quantum Information
Quantum Optics
Gian-Luca Oppo, John Jeffers, Alison Yao (Gordon Robb, Daniel Oi)
Experimental Quantum Optics and Photonics Group
Single-atom imaging
Atom Optics
Nonlinear Photonics
Quantum-cascade lasers 
Stefan Kuhr, Thorsten Ackemann, ER, Aidan Arnold, Paul Griffin, Elmar Haller, Graham Bruce (Nigel Langford)

3. “Noiseless” Quantum State Amplification
Implementation of the “forbidden” transformation
E. Eleftheriadou, SMB and JJ (submitted)
Based on quantum state comparison1 and photon subtraction on coherent states.
Works with high fidelity
and high success probability.
Does not use quantum resources.
Uses already implemented quantum
technology.
1. See P.J. Clarke et al Nature Communications 3, 1174 (2012)

4. Measuring the vacuum state nondestructively
Possible using a V-Stirap System to implement the
measurement
and implementation of “true” photon addition and subtraction
D.K.L. Oi, V. Potacek and JJ, accepted for PRL.

5. Daniel Oi Efficient estimation of quantum states and processes
Characterization of Quantum Devices
Restricted state preparation, control, readout
Signal extraction and parameter estimation
Integration with optimal quantum control
Hitachi Research Labs, Cambridge
Efficient estimation of quantum states and processes
Resource efficient (copies, time, measurements) information extraction
Probes of decoherence, non-Markovian behaviour, spatial and temporal correlation
CubeSats for space-based miniaturized physics experiments
Long-distance quantum entanglement distribution
“Nano-”satellites for fundamental tests of gravity/quantum theory

6. Theory and Simulation at the Quantum Limit
G-L Oppo, G Robb, A Yao
BEC in Optical Lattices at Negative Temperatures
+ Aberdeen and Florence
Optomechanics of
Cold Atoms and BEC
+ T. Ackemann, A. Arnold, E. Riis -4 4 1 2
Can we access
this region? YES
b=1/T

7. Theory and Simulation in Quantum Optics
G-L Oppo, G Robb, A Yao
BEC in Optical Cavities
+ UCL
Exotic States of Orbital Angular Momentum
BEC E
Increasing E
Beams with fractional OAM
Chaotic behaviour
Semi-classical and quantum
theory of OAM states in
parametric down conversion
and OPOs + Glasgow

8. Nonlinear Photonics nonlinearities and complexity in Understand
semiconductor-based photonic devices, especially vertical-cavity surface-emitting lasers (VCSEL)
cold atomic vapors
Understand
Control
Utilize
Dynamics of semiconductor lasers: spatial modes, polarization, spin opto-electronics
Cavity soliton laser: Solitons and semiconductor microlasers
Quantum dot devices: Nonlinear optics, THz, lasers
Terahertz generation by difference frequency
Miller et al., IEEE Sel. Top. QE 7, 210 (2001)
Image of a mesa (p-side) of a broad-area VCSEL like the ones used for cavity soliton laser (from University of Ulm, Ulm Photonics)
Lower image: Very high order mode in a square VCSEL. The off-axis waves are retroreflected into the cavity by a transverse waveguide. To first approximation one can assume that this corresponds to an infinite potential barrier leading to a billiard problem in the classical limit. The very fine fringe scale of the interference indicates a very high mode order or a very high transverse wavevector. In this limit the wave pattern decides to localize along a classical period orbit (white arrows) of a ray reflected by the boundaries. We looked at polarization issue already, Babushkin_PRL_100_213901(2008), but there is interest to extend that and to look at nonclassical correlations between the beams.
Fundamental and applied aspects
Solitons, self-organization: relevance and connections to other areas of Nonlinear Science (interdisciplinary)
collaboration with CNQO group in Dept. of Physics, centre of complex systems at Strathclyde
Example: Quantum billiard in VCSELs:
very high order mode localizes along classical ray trajectory
interest in correlations, polarization, ...
future interest for collaboration: nonlinearities and all-optical switching in the few photons limit

9. Self-organization in cold atoms
87Rb, D2-line, OD  140, T  300 µK, = + 7 
Opto-mechanical self-focusing nonlinearity
feedback from a single mirror: symmetry breaking around a single pump axis
recent observation of coupled light – atomic density patterns
interest to explore quantum optics (correlations, squeezing), sub-recoil limit and quantum matter
Light pattern
Density pattern

10. Cavity solitons
cavity soliton = (spatially) self-localized, bistable solitary wave in a cavity
Each of the solitons is a bistable microlaser
Soliton 5 
Pumped laser aperture 200 m
Interpretation of soliton: VCSEL: planar planar cavity, only marginally stable
Soliton = self-induced mode, self-sustained by self-lensing
First semiconductor based cavity soliton laser was demonstrated by my group: Tanguy et al., PRL_100_013907(2008); 52 citations
All-optical manipulation and control:
Demonstration of all 8=23 bit states of three solitons by external laser (red)
All-optical processing
Fundamentals of self-organization (interdisciplinary)

11. Young’s double slit with atoms
Two separate BECs in magnetic trap with optical dipole barrier
Spaced by up to 0.25 mm
Released and magnetically levitated
Allowed to interfere
Observe with absorption imaging
High visibility fringes
Need to demonstrate control of phase of two condensates
Independent control of phase of one component  measurement device
1500750mm
Optical plug+160ms ‘levitation’
95% contrast
Zawadzki et al PRA 81, (2010)

12. Inductively coupled ring traps
Sagnac interferometer?
Δ𝜑= Ω ∙ 𝐴 2 𝐸 𝑟 ℏ 𝑐 2
Time averaged potential:
Smooth
Adiabatic
Scalable
𝐸 𝑟,𝑎𝑡𝑜𝑚 𝐸 𝑟,𝑝ℎ𝑜𝑡𝑜𝑛 = 𝑚 𝑐 2 ℏ 𝜔 ≈ 10 11
B(t)
What next?
New design (rring=1.6mm)
Atom interferometry
Michelson
Sagnac
Pritchard et al.,
New Journal of Physics (2012)

13. The simple Magneto-Optic Trap
MOT: great starting point for cold atom experiments, but…..
Vision – can we make an optical component, that with one incoming beam generates all other beams required for the MOT (with the correct polarisations)? i.e. make the MOT useful.
Etched binary gratings
If d < 2 only 0th and 1st orders
If etch depth is /4 0th order is suppressed
Problem: 20% loss

14. Results and way forward
Patterns tested:
Performs as expected: 108 atoms, 50 µK
Nature Nanotechnology (May 2013)
Potential: Cold atom based measurement devices
Challenge: Lossless gratings?
Potential collaboration with Erlangen?

15. Atoms in optical lattice
Optical lattices with single-particle access S. Kuhr (Strathclyde) / I. Bloch (MPQ)
Atoms in optical lattice
J. F. Sherson et al., Nature 467, 68 (2010)

16. Single-particle acess
Single-spin addressing
C. Weitenberg et al., Nature 471, 319 (2011)
See also:
C. Weiterberg et al., PRL 106, (2011)
M. Endres et al., Science 334, 200 (2011)
M. Cheneau et al., Nature 481, 484 (2012) M. Endres et al., Nature 487, 454 (2012)
P. Schauß et al., Nature 491, 87 (2012)
T. Fukuhara et al., arXiv: v1(2012)
Experiments with atoms in optical lattices are brought to a new level!
 Each atom in an ensemble of hundreds of particles can be detected and manipulated individually!

17. Setups at Strathclyde / MPQ
Single-site imaging for fermionic (Strathclyde) and bosonic atoms (Strathclyde/MPQ)
double species 3D-MOT 87Rb+40K
+ magnetic trap
double species 2D-MOT 87Rb+40K
Magnetic colis (up to B = 600 G) to control ) F = 9/2 /(mF = 7/2, mF = 9/2) state B = 202 G
‘‘Science region‘‘
optical lattices
microscope
Feshbach coils

18. Objectives within the IMPP
Development/improvement of techniques for single-atom imaging, manipulation and detection (single-qubit rotations in stabilized magnetic field environments)
Creation and characterization of entanglement with cold atoms
 Many-particle entanglement in many-body systems
 Two-qubit quantum gates using spin-dependent transport (Strathclyde)
 Rydberg atoms for long-range interactions (MPQ), quantum gates and the creation of mesoscopic entangled states
IMPP Proposal:
We will explore the various possibilities of creating many-particle entangled states either, e.g., in spin-dependent lattices, through coherent splitting of Bose-Einstein condensates or mesoscopic Rydberg gates. The unique possibilities of detecting individual quantum particles can be used to characterise these states with unprecedented precision. In the matter-wave interferometers, work will be extended from bosonic systems to fermions, where the lack of interatomic interactions will also lead to increased precision. Atom interferometers can be configured as gravitational sensors with applications ranging from navigation and geodesy to gravitational wave detection