Transcript Quantum Information Related Optics Research @ UBC Physics

Quantum Information Related
Optics Research @ UBC
Physics and Astronomy
Jeff Young et al.
Kirk Madison et al.
David Jones et al.
Department of Physics and Astronomy
University of British Columbia
Three Principal Areas
• Optical lattices (Kirk Madison)
– Simulating complex quantum problems
• Photonic crystal/quantum dot-based
nonlinear optics (Jeff Young)
– Towards QED on-a-chip
• Phase-controlled laser sources (David
Jones)
– Coherent control
Quantum materials research with
ultra-cold atomic gases
Kirk Madison
Theme : An ensemble of ultra-cold atoms held in optical potentials can be used to
experimentally realize and study certain model Hamiltonians
Directions : Realize N-body quantum systems of fundamental interest to condensed
matter physics - low dimensional and/or strongly correlated systems - examples
include
• 1-D chains - (Luttinger liquids and Tonks gas)
• 2-D and 3-D Hubbard (lattice) models
with bosons and/or fermions
proof of principle : recent experimental realization of the Bose-Hubbard model
Goal : study the behavior of various model Hamiltonians to determine the essential
“ingredients” (terms in H) of new and/or unexplained phenomena - examples include
• high-Tc superconductivity
What is its connection (if any) to the Fermi-Hubbard model?
Periodic optical potentials are the
analog of ionic crystal potentials
- the optical-dipole potential experienced by an atom (AC stark shift) is proportional to
the laser intensity
- an intensity standing wave can be made by interfering two monochromatic lasers
Intensity = |E1 + E2|2 = I1 + I2 + 2(I1I2)1/2 cos[(k1-k2)•r]
k2
k1
E2
periodicity d = l/2 sin(q/2)
E1
in this example
q = p , d = l/2
d
Designer Potentials:
• the depth (intensity), position (phase), and periodicity (wave vectors) of the potential
can be controlled by changing the properties of the interfering beams
• the topography can also be changed by adding more beams
• linear gradients can be added using external fields (gravitational, magnetic)
The connection to electronic condensed matter
systems is by analogy
atom
analogous to
optical lattice
ionic crystal
collisional interaction
spatial rotations
electron
Coulomb interaction
in some cases
Notable differences:
• optical lattices possess (almost) perfect crystal order
no phonons, no impuries, no dislocations
but “imperfections” can be added in...
• the atoms considered here are neutral
but mass ~ equivalent to charge d.o.f.
magnetic fields
The connection to theoretical model systems is more direct
proof of principle : recent experimental realization of the Bose-Hubbard model
Greiner, Mandel, Esslinger, Haensch, and Bloch
“Quantum phase transition from a superfluid to a Mott
insulator in a gas of ultracold atoms”, Nature 415, 39 (2002)
new and relevant proposals to observe other effects with cold atoms abound
Hofstetter, Cirac, Zoller, Demler, and Lukin
“High-Temperature Superfluidity of Fermionic Atoms in Optical
Lattices”, Phys. Rev. Lett. 89, 220407 (2002)
A major contribution that experiments with ultra-cold atomic gases could make
is to “bridge the gap” between models and real materials
Integrated (Nonlinear) Optical
Circuits
• Based on highly-evolved silicon-on-insulator and
III-V semiconductor wafer processing technology
(optical steppers, tight tolerances)
• High-Q, ultra small volume microcavities defined
by lithography and etching (ie. engineerable)
• Integrate with artificial quantum dots to achieve
nonlinear optics at the single photon level
Ideal Design Scenario…
PC Inside
Cavity
Bend
I/O Coupler
Optical
Transistor
SOI Sample Geometry
100 fs OPO
(200 nm x 450 nm Si channels)
Galian Photonics Inc.
Nanostructured Microcavity embedded
in Single Mode SOI Waveguide
Photoresist
~1 mm
1 mm
Si, 200 nm
SiO2
Si substrate
2 mm
Cowan, Rieger and Young, Optics Express (in press)
3D Microcavities in Waveguides
Bandgap of barriers
|a>
|b>
Q~ 250
Photonic crystal tunneling barriers
|b>
|a>
Add PbSe Quantum Dots to Enhance
Nonlinear Susceptibility in Cavity
Photoresist
~1 mm
1 mm
Si, 200 nm
SiO2
Si substrate
2 mm
Soon to be Integrated
Murray McCutcheon, in progress
Close Up
Q~10,000
Green’s Function
FDTD
Minimize Switching Power Using 1D
Waveguide + Nonlinear 0D Defect Cavity
I ()
R()
T()
Lorentzian Bistability (no background)
Q  4000 Vmode=0.055 mm3
Power  15 mW
Soljacic et al., PRE 66, 055601(R) 2002
Cowan and Young, PRE 68, 46606, 2003
lb2/n2 0, 0.1 & 0.4
Nonlinear Cavity Effect with QDots
Q~1200
Transmission (a.u.)
Pumped on resonance
Pumped off resonance
Cowan, in progress
Energy (cm-1)
Optical Waveform Synthesis (David Jones)
Phase-stabilized fs lasers are used to engineer coherent electric field waveforms
at optical (300-600 THz) frequencies with well-defined optical phases
Controlling the carrier-envelope phase (fCE)
fCE
Combined with pulse shaping techniques
f
f
f
lens
f
lens
grating
grating
spatial light
modulator (SLM)
input pulse
shaped pulse
Leads to…
• Analog optical signal processing
• Coherent control of atomic, molecular, and semiconductor systems
• Designer (…and electric field coherent) optical pulses for selective probing of
chemical reactions
• Quantum information…? (very likely)
LUX - Laser Systems
Laser-based timing system
- femtosecond x-ray pulses derived
from laser pulses or laser-based RF
Master Oscillator
Laser + RF
Interconnected femtosecond laser systems
- actively synched or seeded from master
Maintain <100 fs synchronization
- laser to laser synchronization
- stabilized timing distribution network
HGHG FEL
Seed Laser
distribution network
crab cavity
Photo Injector
Laser
Multiple
Beamline Endstation
Lasers
LINAC RF
R. Schoenlein LUX Review 4/28/03
Summary
• UBC Physics and Astronomy has a
number of optical research activities that
are directly relevant to quantum
information technologies
Acknowledgements: NSERC, CIAR, Galian Photonics Inc., CFI, BCKDF
Spectra: 800 mm Long Single Mode
20:1 Negative Differential Transmission
Using In-line Filter
Distribution of Time/Frequency Standards
Plentywood
Time/frequency ?
Known
time/frequency
Increase in
stability
How do you compare time/frequency?
• Transport clock
• via GPS/ two way satellite transfer
• optical fiber link
Motivation for high stability time/frequency transfer
• Comparison of optical standards for fundamental physics,…
• Remote pulse synchronization: Laser and Linac http://bc1.lbl.gov/CBP_pages/CBP/groups/LUX/
• Surveillance
• Telecom network synchronization