Sources, Memories, Detectors

1
Sources, Memories, Detectors

• Ryan Camacho, Curtis Broadbent,
• Michael Pack, Praveen Vudya Setu, Greg Armstrong,
  Benjamin Dixon and
• John Howell
• University of Rochester
• Collaboration with Bob Boyd

Thanks to DARPA, ARO, PECASE, NSF, Research
Corporation, ARO MURI, DURIP, University of
Rochester
2
Group
3
Overview

• Goals
• Sources, Memories and Readout of Quantum Images
• Quantum Buffering
• Stopped Images (gt1000 pulse delays)
• Entanglement Preservation
• Time-energy Biphoton Absorption
• Image Readout

4
Sources, Memories and Detection
Source
Memory
Detection

• Source produces quantum images
• Memory stores image
• Images are Eigenstates of detection

5
Memories
Cesium Resonances and Delays

• Use steep linear dispersion between two
  absorption resonances to slow down Quantum and
  Classical Images
• Preserve Images (not just binary signals) for
  large delays
• Ultra-low noise (preserve quantum fields in low
  loss regime)
• Doppler broadened vapors
• Have delayed 275 ps pulses in excess of 10 ns and
  740 ps pulses in excess of 60 ns.
• Small broadening Dispersive broadening dominates
  absorptive broadening.

Macke et al., Phys. Rev. A 73, 043802 (2006).
H. Tanaka et al., Phys. Rev. A 68, 053801 (2003).
Linear Circuits
Camacho et al., Phys Rev Lett 98, 153601 (2007)
6
Image Buffering Experiment
Camacho et al, Phys. Rev. Lett. 98, 043902 (2007)
7
Classical Image Interference

• Matched image pulses (high fringe visibility)
• Unmatched image pulses (low

Local oscillator pulse and slow light pulse
arrive at same time at the beam splitter
(interference)
Arrive at different times
8
Weak Coherent State 2-D Imaging
3ns delay of 2-d image, 0.8 photons per pulse and
(right) 2d image propagating through air, 0.8
photons per pulse.
9
(No Transcript)
10
Weak Coherent State 1-D Imaging
0.5 photons, on average, per pulse hit a 2 bar
test pattern. The image pulses are delayed by 9
ns. A multimode fiber is used to scan the image.
11
Entanglement Preservation in Buffer
5p3/2
5p1/2
5s1/2
12
(No Transcript)
13
Potential

• Digital signal processing
• Holography
• Remote imaging
• Quantum buffers
• Scenedow?
• Etc.

14
Stopped Light
Vapor Cell with Buffer Gas
15
Slow Light Experiment
16
EIT Feynman Diagrams
3gt
2gt
1gt
17
Stopped Light Results
Pump turned off
Pump turned on
18
Stopped Light In Hot Vapors
1000 delays
19
Stopping Transverse Quantum Images

• Developing a transverse image storage device for
  quantum images
• Stack Multiple Images in the medium
• Readout any image in the stack at will Images on
  demand

20
Energy-Time Quantum Cryptography Simplified View
PPS Passive Power Splitter RS Raw Sync
Alice
Type-I BBO
Bob
50mW cw _at_390nm
50/50 Fiber BS
l/2
l/2
PBS
PBS
50/50 BS
50/50 BS
Sync Generator
A2
A1
B1
B2
RS
Time Stamping
Time Stamping
PPS
Computer B
Computer A
Internet
21
Time-Time Correlations

• Multistate state cryptosystem.

Large Bin
0123
Synch Pulses ever 64 ns
Alice and Bob both measure their Photon at the
same point in the time bin
Alice
Bob
Time bin
0,34,25,92,45
0,34,25,92,45
22
Sifted Key Bit Rates Qudit to Qubit conversion
Example 1024 alphabet qudit converted to 10 bits
I. Ali Khan, C. Broadbent, J.C. Howell, PRL 98,
060503 (2007)
23
Franson Interferometer Measure Energy
Correlations
Output ports of Michelson with postselection of
short-short and long long
QND Measurement
Using temporal commutator relation, normal
ordering and assuming l1l2
24
Franson Visibility as a function of Eves
measurement in time for Gaussian POVM
3 meters
Fringe Visibility
10 meters
Eves Temporal Uncertainty for QND
25
Biphoton Absorption
Rb
Dwpump1 MHz
5D5/2
idler
5p3/2
Dwpdc10 THz
signal
5s1/2
26
Two Photon Absorption in Fiber Nanotapers and
Holey Fibers

• Evanescent Field Coupling or Mode confinement
• Small mode volume
• Linear Biphoton Intensity response
• Switching
• Close to Completion

27
Conclusions

• Delayed transverse image in slow light medium
  preserved amplitude and phase
• Low noise, linear device useful for quantum
  information preservation.
• Demonstrated multiple pulse delays with little
  pulse distortion.
• Slow Light FTI, Preservation of quantum signals,
  and 1000s of pulse delays
• Many interesting possibilities
• Gravitometry
• Stopped Images

28
Recent Work