building a qkd network out of theories and devicesmath.bu.edu/people/jaeger/pearson.pdfcooled apds...
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Building the DARPA Quantum Network
HarvardUniversity
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Building a QKD Network
out of Theories and DevicesDecember 17, 2005
David Pearson
BBN Technologies
HarvardUniversity 2
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Why QKD? Why now?
• Unconditional security, guaranteed by the laws of physics, is very compelling
• Public-key cryptography gets weaker the more we learn – even for classical algorithms
• If we had quantum computers tomorrow we’d have a disaster on our hands.
• Future proofing – secrets that you transmit today using classical cryptography may become vulnerable next year (RSA ’78 predicted 4 x 109 years to factor a 200-digit key, but it was done last May)
• The technology of QKD seems to be mature enough that we can start to create usable systems.
HarvardUniversity 3
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
DARPA Quantum Network - Goals
QKDEndpoint
Encrypted Trafficvia Internet
QKDEndpoint
QKD Switch QKD Switch
QKD Switch
QKD Switch
QKD Repeater
PrivateEnclave
PrivateEnclave
Ultra-Long-Distance Fiber
End-to-End Key Distribution
We are designing and building the world’s first Quantum Network, delivering end-to-end network security via
high-speed Quantum Key Distribution, and testing that Network against sophisticated eavesdropping attacks.
As an option, we will field this ultra-high-security network into commercial fiber across the metro Boston area and
operate it between BU, Harvard, and BBN.
We are designing and building the world’s first Quantum Network, delivering end-to-end network security via
high-speed Quantum Key Distribution, and testing that Network against sophisticated eavesdropping attacks.
As an option, we will field this ultra-high-security network into commercial fiber across the metro Boston area and
operate it between BU, Harvard, and BBN.
HarvardUniversity 4
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
DWDM
Adjustable Air Gap Delay
E-OPhaseShifter
DAC
1550.92 nmSync PulseReceiver
50 / 50 Coupler
LinkFiber
φ
1550.12 nmQKD
Cooled APDs
Receiver (Bob)
Amp
D1D0
D1D0
D1D0
ReceiverOPC DIO Card F
FF
DelayLoop
November 5, 2003
2 PulseThresholds
3-WaySplitter
Gates
Circulator
FaradayMirrors
Amp
B
BB
B
BB
14 BitsSYNC
1550.12 nmQKD
Data Laser
OpticalAttenuator
50 / 50Coupler
E-OPhaseShifter
1550.92 nmSync LaserDelay
Loop
DWDM
Delay Line
φ
Transmitter (Alice)
10 MHzClock
F
FF
VB
VBVB
TransmitterOPC DIO Card 0
10
DAC
Polarizer
C
CC
PulseGenerator
SignalSplitter
Gate
SignalSplitter
TTL
NIMDelay Line
3Pulse
Generators
BufferingBuffering
SignalSplitter
PulseGenerator
trig.
trig.
14 Bits
PB
PBPB
DelayLoop
Adjustable Air Gap Delay
PulseThreshold
‘Mark 2’ Weak Coherent QKD Links4 Nodes Continuously Operational Since October 2003
• Polarization Independent • Sync & Data at 1550 nm• Active Path Length Control
HarvardUniversity 5
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
QKD Software Suite and Protocols
VPN
Internet (public channel)
SAD
EthernetDeviceDriver
EthernetDeviceDriver
IKE
SPD
OpticalProcess Control
Interface
Optical Hardware
EthernetDeviceDriver
IP
QKD Endpoint
IPsec
QKD Protocols
Entropy Estimation
PrivacyAmplification
Authentication
Sifting
Error Detectionand Correction
HarvardUniversity 6
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Status as of 3½ Years Ago
DARPA QuIST
Network Testbed
Goes Here
DARPA QuIST
Network Testbed
Goes Here
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
The Year 1 Weak-Coherent Link
Alice
Bob
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
The Cooled Detector Package
2 Epitaxx detectors
(EPM 239 AA SS )
Dual Peltier coolers
Approx. 2 x 10-2 Torr
Operates near –60 C,
achieves –80 C max
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Time in Hours, Data Segment ended 2 Jan 03
First Days Up and Running
Days in Continuous Operation
Typical(Untuned)
QBERRange
Errors Per Properly-Sifted Detect EventGood Sifted Bits / Pulse (Untuned System)
D0
D1D0
D1
Mean emission = 0.1 photons/pulse;Perfect results would be 0.05; 10% quant. Eff. would be 0.005
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Bounding Eve’s Information(the heart of QKD)
Classical ChannelALICE
BOB
EVE
Information Eve learns:t Bits from probing single-photon pulsesq Classical bits leakedν
Bits from imperfect quantum channel
Quantum Channel
After we get the bound, we use privacy amplification to reduce Eve’s knowledge to
ε<< 1
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Imperfections in the Quantum Channel(taking security proofs w/ a grain of salt)
• Multi-photon pulses (weak coherent ≠ single photon)• Unbalanced detectors• Timing imperfections in detectors• Active probes of Alice/Bob interferometers (OTDR)• Breakdown flash from APDs• Memory effects of APDs
...
A consensus list of vulnerabilities would be a very valuable thing!
Some of the vulnerabilities we want to fix in the optics, some by monitoring, and some by privacy amplification (with extensions to the proofs)
Alice Bob
Low-loss channel
Quantum memoryEve Eve splits off one photon from any
multi-photon pulse, keeps one in a quantum memory and sends the other through to Bob over a special low-loss channel. If she doesn’t get a photon, she blocks the pulse. When bases are announced she measures her stored qbit in the correct basis
HarvardUniversity 12
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Imperfections in the Quantum Channel(taking security proofs w/ a grain of salt)
• Multi-photon pulses (weak coherent ≠ single photon)• Unbalanced detectors• Timing imperfections in detectors• Active probes of Alice/Bob interferometers (OTDR)• Breakdown flash from APDs• Memory effects of APDs
...
A consensus list of vulnerabilities would be a very valuable thing!
Some of the vulnerabilities we want to fix in the optics, some by monitoring, and some by privacy amplification (with extensions to the proofs)
D0
D1
HarvardUniversity 13
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Imperfections in the Quantum Channel(taking security proofs w/ a grain of salt)
• Multi-photon pulses (weak coherent ≠ single photon)• Unbalanced detectors• Timing imperfections in detectors• Active probes of Alice/Bob interferometers (OTDR)• Breakdown flash from APDs• Memory effects of APDs
...
A consensus list of vulnerabilities would be a very valuable thing!
Some of the vulnerabilities we want to fix in the optics, some by monitoring, and some by privacy amplification (with extensions to the proofs)
Detector sensitivity
Time
Eve injectspulse here
D0
D1
HarvardUniversity 14
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Imperfections in the Quantum Channel(taking security proofs w/ a grain of salt)
• Multi-photon pulses (weak coherent ≠ single photon)• Unbalanced detectors• Timing imperfections in detectors• Active probes of Alice/Bob interferometers (OTDR)• Breakdown flash from APDs• Memory effects of APDs
...
A consensus list of vulnerabilities would be a very valuable thing!
Some of the vulnerabilities we want to fix in the optics, some by monitoring, and some by privacy amplification (with extensions to the proofs)
Alice
LinkFiber1550.12 nm
QKDData Laser
OpticalAttenuator50 / 50
Coupler
E-OPhaseShifter
1550.92 nmSync LaserDelay
Loop
DWDM
φ
PolarizerAdjustable Air Gap Delay
Eve
HarvardUniversity 15
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Imperfections in the Quantum Channel(taking security proofs w/ a grain of salt)
• Multi-photon pulses (weak coherent ≠ single photon)• Unbalanced detectors• Timing imperfections in detectors• Active probes of Alice/Bob interferometers (OTDR)• Breakdown flash from APDs• Memory effects of APDs
...
A consensus list of vulnerabilities would be a very valuable thing!
Some of the vulnerabilities we want to fix in the optics, some by monitoring, and some by privacy amplification (with extensions to the proofs)
HarvardUniversity 16
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Imperfections in the Quantum Channel(taking security proofs w/ a grain of salt)
• Multi-photon pulses (weak coherent ≠ single photon)• Unbalanced detectors• Timing imperfections in detectors• Active probes of Alice/Bob interferometers (OTDR)• Breakdown flash from APDs• Memory effects of APDs
...
A consensus list of vulnerabilities would be a very valuable thing!
Some of the vulnerabilities we want to fix in the optics, some by monitoring, and some by privacy amplification (with extensions to the proofs)
HarvardUniversity 17
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Howard Brandt’s entangling probe for BB84
(quant-ph/0509088)
Uses an entangling probe with a POVM which can sometimes unambiguously discriminate between 0 (in either basis) and 1. With loss, allows PNS-type attack for true single-photon source
Shapiro showed that Brandt left out part of the error rate (thank goodness!)
But it was plausible that the attack worked, despite the proofs
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Quantum Networking
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Quantum Networking
• Without a network, QKD will never “take off”
• The holy grail: using quantum teleportation and quantum memory to switch qbits– Could extend range of quantum communication
through entanglement purification– At least 10 years off
• An interim solution: circuit-switched quantum links using optical switches
• Another useful technology: key relay through trusted intermediate nodes
HarvardUniversity 20
Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Two Kinds of QKD NetworkingCurrently Operational in DARPA Quantum Network
• Switched networks– Share infrastructure – Quite secure – Requires compatible
technology– Limited in range
• Trusted networks– Can extend range– Allow different kinds of
QKD to play together– Robust and redundant– Nodes must be kept
secure
QKD
QKD
Freespace links
QKD
QKD
QKD
QKD
QKD
QKD
Switched fiber w/ phase modulation
Switched plug & play fiber links
Entangled link in fiber
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Optical Switching in DARPA Quantum NetworkNodes Do Not Need to Trust the Switching Network
AliceAlice BobBob
BorisBoris
QuantumOptical
Network
Pairwise QKD Key Material Built Up Between . . .
Alice & Bob Alice & Boris
Anna & Bob Anna & Boris
AnnaAnna
Suitable for Compatible QKD Nodes at Metro Distance sSuitable for Compatible QKD Nodes at Metro Distance s
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Key Relay in DARPA Quantum NetworkNodes Do Need to Trust the Relays
AliceAlice BobBob
AnnaAnna
Pairwise QKD Key Material Built Up Between . . .
Alice & Ali (via Boris as relay)
Bob & Boris (via Alice or Anna as relay)
FiberOptical
Network
Suitable for Incompatible QKD Nodes or Long Distanc e RelaySuitable for Incompatible QKD Nodes or Long Distanc e Relay
AliAli
Fiber orFreespace
BorisBoris
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
The DARPA Quantum Network
Operating Continuously Across Cambridge Since 6/200 4
+ Freespace link + Entangled link
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DARPA Quantum Network in OperationStatistics Captured Nov. 1, 2004
Alice / Boris(BBN-BU)11.5 dB, 19.6 km
mu = 1.0QBER ~ 7.6%
~ 160 bits/sec
Anna / Boris(Harvard-BU)16.6 dB, 29.8 km
mu = 0.5QBER: N/A
0 bits/sec
Alice / Bob(Within BBN)0 dB, 0 km
mu = 1.0QBER ~ 2%
~ 13,000 bits/sec
Anna / Bob(Harvard-BBN)5.1 dB, 10.2 km
mu = 0.5QBER ~ 3.5%
~ 1,000 bits/sec
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Cambridge Dark Fiber
Many connectors in current path to BU (Boris) resulting in high atten. Will splice in coming months, but this gives a preview of mid-distance (~50 km) performance.
BUBUHarvardHarvardBBNBBN
1.2 dB loss
1.2 dB loss
300 Bent St.
19.6 km
11.5 dB
BU
10.2 km5.1 dB
Harvard
19.6 km
11.5 dB (b)
10.2 km
5.1 dB (a)
BBN
BUHarvardBBN
Distances & Attenuations
(a) Equivalent to 24.3 km fiber span at 0.21 dB/km(b) Equivalent to 54.8 km fiber span at 0.21 dB/kmBoth measurements include 2x2 fiber switch in path (~1 dB).
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Routing and Key Relay
• Determines topology of network
• Chooses paths with small number of nodes, and ample key material
• Uses one-time-pad encryption of new key• Transports keys, not data
A simple network
• Each node knows full network topology
• Can choose shortest path
• Or multiple independent shortest paths
A
C
B
D
G H
E F
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Open Testbed for
QKD Networking
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
BBN’s QKD ProtocolsModular Suite of QKD Protocols
VPN
Internet
SAD
EthernetDeviceDriver
EthernetDeviceDriver
IKE
SPD
OpticalProcess Control
Interface
Optical Hardware
EthernetDeviceDriver
IP
QKD Endpoint
IPsecQKD Protocols
Entropy Estimation
Entropy Estimation
PrivacyAmplification
PrivacyAmplification
AuthenticationAuthentication
SiftingSifting
Error Detectionand Correction
Error Detectionand Correction
Entropy Estimation
PrivacyAmplification
Authentication
Sifting
Error Detectionand Correction
IPsec Based� Public Key� Secret Key
� GF[2n] Universal Hash
� BBBSS 92� Slutsky� Myers / Pearson� Shor / Preskill
� BBN Cascade� BBN ‘Niagara’ FEC
� Traditional� ‘SARG’ Sifting
Simple, Open Interface Makes It EasyTo “Plug In” Other Teams’ QKD Systems
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Open InterfacesEnable a wide range of Quantum channels
QKD Protocols
Entropy Estimation
PrivacyAmplification
Key Exchange
Sifting
Error Detectionand Correction
QKD emulator
BBN Weak-Coherent link
Std. interface
BBN Entangled link
Qinetiq Free-space link
NIST high-speed free-space link
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
The ‘Mark 2’ QinetiQ Freespace Link
• Background Information– Based on Successful QinetiQ / Munich Freespace
System– New QinetiQ Transmitter, with Subcontract for
Improved Munich Detector
• Current Status– Brassboard Transmitter Demo’d with Old Receiver– BBN Software Integrated with QinetiQ System– Continuous Operation across QinetiQ Laboratory– Delivered and operational March 23, 2005
23 km demonstrated through free space
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
NIST / BBN Freespace CollaborationAli & Baba – What is Currently Integrated in BBN’s Lab
Quantum Telescope840nm (don’t have)
Ali
Classical Telescope1550nm (not yet)
Quantum Telescope840nm (don’t have)
Classical Telescope1550nm (not yet)
VPN
Internet
SAD
EthernetDeviceDriver
EthernetDeviceDriver
IKE
SPD
OpticalProcess Control
Interface
EthernetDeviceDriver
IP
QKD Endpoint
IPsecQKD Protocols
Entropy Estimation
Entropy Estimation
PrivacyAmplification
PrivacyAmplification
AuthenticationAuthentication
SiftingSifting
Error Detectionand Correction
Error Detectionand Correction
Entropy Estimation
PrivacyAmplification
Authentication
Sifting
Error Detectionand Correction
IPsec Based� Public Key� Secret Key
� GF[2n] Universal Hash
� BBBSS 92� Slutsky� Myers / Pearson�Shor / Preskill
� BBN Cascade� BBN ‘Niagara’
� Traditional� ‘Geneva’ Sifting
Baba
Quantum and Classical Channels running through Coax
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Open Interface to OpticsEnables a wide range of Quantum channels
QKD Protocols
Entropy Estimation
PrivacyAmplification
Key Exchange
Sifting
Error Detectionand Correction
QKD emulator
BBN Weak-Coherent link
Std. interface
BBN Entangled link
Qinetiq Free-space link
NIST high-speed free-space link
NIST high-speed free-space link:100 – 300x as fast as other systems.
Currently BBN software discards most frames due to rate mismatch with reconciliation
Bottleneck - Cascade Error Correction
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
BBN’s ‘Niagara’ LDPC Forward Error Correction40x Less Comms Overhead, 16x Less CPU than Cascade
Inputs
k (block size) 1, 0, 0, . . . 10, 0, 1, . . . 0
:0, 1, 0, . . . 0
A low-density parity-check matrixPseudo-random seed
D – density profile
p – number of parity constraints
(revealed bits)
Code
historic error rate
noise margin
margin for suboptimal
code
Random, with constraints on row/column weights
A promising alternative to adding a safety margin is to add more parity bits when
decoding fails
126%120%% of Shannon limit
1.117.4CPU usage (secs / Mb, 800MHz x86)
48019200Communication (bytes)
168Delay (round trips)
1006958Revealed bits
LDPCBBN CascadeAverage for 4096 bit blocks, 3% error rate
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Detectors
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IBM Almaden CollaborationNewest BBN QKD Systems Incorporate IBM Detectors
0 5 10 15 20 25 30 35
1E-7
1E-6
1E-5
1E-4
1E-3
EPM239-0131T2019
Dar
k C
ount
s / B
ias
Pul
se
QE (%)
273 K 251 K 232 K 220 K
0 5 10 15 20 25 30 35 401E-3
0.01
0.1
1
10 EPM239-0131T2019
Afte
rpul
se P
roba
bilit
y (%
)
Blanking Time (µs)
220 K (5 MHz) 220 K (2.5 MHz) 200 K 210 K 220 K 230 K
Donald S. Bethune, William P. Risk and Gary W. PabstIBM Almaden Research Center
San Jose, CA
IBM Almaden supplied Detectors for DARPA Quantum Network QKD systems
IBM Almaden supplied Detectors for DARPA Quantum Network QKD systems
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
BBN / U. Rochester / NIST Detector CollaborationFrom University Demonstration to the Telecom Closet
Single BridgeMeanderStructure
Superconducting (4.2 K) NbN hot-electron photodetector (HEP) with picosecond response time, high intrinsic quantum efficiency, negligible dark counts, and the capability to detect single photons from the ultraviolet to the infrared wavelength range.
Fabrication and Properties of an Ultrafast NbN Hot-Electron Single-Photon Detector,” R. Sobolewski, LLE Review, Volume 85, p. 34.
Sumitomo
Goal: Engineer Very High Speed Single Photon Detectors
Goal: Engineer Very High Speed Single Photon Detectors
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Why Develop this Detector?
Detector Model
Count rate(Hz)
QE %
Jitter (ps)
Dark Counts (per ns)
InGaAs PFD5W1KS APD (Fujitsu)
5 x 106 >20 >200 6 x 10-6
R5509-43 PMT (Hamamatsu)
9 x 106 1 150 1.6 x 10-5
Si APD SPCM-AQR-16 (EG&G)
5 x 106 0.01 350 2.5 x 10-8
Mepsicron-II (Quantar)
1 x 106 0.01 100 1 x 10-10
Transition Edge Sensor (NIST)
2 x 104 >80 N/A ~0
SSPD projection (R. Sobolewski)
3 x 109 >10 18 1 x 10-11
Ideal Characteristics for Quantum Key DistributionVery Fast (> 1 GHz), Low Dark Count (< 1/s), Good Q E (>10%)
Ideal Characteristics for Quantum Key DistributionVery Fast (> 1 GHz), Low Dark Count (< 1/s), Good Q E (>10%)
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
Theories vs. Devices
When you sit down to engineer a QKD system to meet those security guarantees, you constantly have to bridge the abstract world of the proofs and the messy world of devices
Justice? You get justice in the next world, in this world you get the law. – William Gaddis
Proofs? You get proofs in the next world, in this world you get devices. – Chip Elliott
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Building the DARPA Quantum NetworkCopyright © 2005 by BBN Technologies.
HarvardUniversity
Active Collaborations in Year 4
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The Team
Boston UniversityProf. Alexander Sergienko
Prof. Mal Teich
Prof. Bahaa SalehProf. Gregg Jaeger
Dr. Martin JaspanDr. Gianni Di GiuseppeDr. Hugues De Chatellus
Harvard UniversityProf. Tai Tsun Wu Dr. John M. Myers
Dr. Dionisios Margetis
Dr. F. Hadi MadjidMargaret Owens
BBN TechnologiesDr. Alex Colvin
Chip ElliottDr. Chris Lirakis
John Lowry
Dr. David PearsonOleksiy Pikalo
John Schlafer
Dr. Greg Troxel
Henry Yeh
VisitorsRich Cannings (U. Calgary)
University of RochesterProf. Roman Sobolewski
NIST BoulderDr. Aaron MillerDr. Sae Woo Nam
Dr. Robert Schwall
1060204 %d0%bb%d0%b8%d1%81%d1%82%d0%be%d0%b2%d0%ba%d0%b0 %d0%bf%d0%be %d1%82%d0%b5%d0%bf%d0%bb%d0%be
%d0%92%d1%96%d0%b4%d0%bf%d0%be%d0%b2%d1%96%d0%b4%d1%8c %d0%9e%d0%b1%d1%83%d1%85%d1%96%d0%b2 %d0%bf%d
%d0%9d%d0%b0%d0%b2%d1%87%d0%b0%d0%bb%d1%8c%d0%bd%d0%be %d0%bc%d0%b5%d1%82%d0%be%d0%b4%d0%b8%d1%87%d0
%d0%a4%d0%93%d0%9e%d0%a1%203 %20%d0%9b%d0%b5%d1%87%d0%b5%d0%b1%d0%bd%d0%be%d0%b5%20%d0%b4%d0%b5%d0%b