Networking Problems in Using Quantum Repeaters Rodney Van Meter MAUI, 2009/4/16 [email_address] http://www.sfc.keio.ac.jp/...
Assume a Quantum Computer  Like This...
I want to Build a Distributed Quantum System Like This Laboratory-sized quantum multicomputer or transcontinental network,...
Repeater Protocol Stack Van Meter  et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear), quant-ph:0705.4128  Phys...
Outline <ul><li>Two types of quantum networks </li></ul><ul><li>IPsec with QKD </li></ul><ul><ul><li>IPsec with QKD </li><...
Two Types of Quantum Networks Unentangled Networks Entangled Networks A B C E G H
Quantum Key Distribution (QKD) <ul><li>Creates a  shared, random secret   between two nodes </li></ul><ul><li>Uses physica...
IPsec with QKD (ORF2008)‏
The DARPA Quantum Network slide from Elliott, BBN
SECOQC Prototype - principle layout Slide from M. Peev, 2008 FOR 81 m LMU
A Trusted repeater QKD-Network: Abstract Architecture (SECOQC, Europe) Slide from M. Peev, 2008 QKD  Access Node QKD Core ...
QKD with IPsec Plans <ul><li>Test over raw fiber, Yagami<->K2 </li></ul><ul><li>Use key for one-time pad </li></ul><ul><li...
Outline <ul><li>Two types of quantum networks </li></ul><ul><li>IPsec with QKD </li></ul><ul><ul><li>IPsec with QKD </li><...
Network Link Technology (Qubus)‏ coherent optical source (laser)‏ waveguide homodyne detector transceiver qubit in node 1 ...
Quantum Repeater Operation: Entanglement Swapping Station 0 Station 1 Station 2 Bell State Measurement Fidelity decreases;...
Nested Entanglement Swapping
Purification Station 0 Station 2 Results must be communicated  (two-way?)
Repeater Protocol Stack Van Meter  et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear), quant-ph:0705.4128  Phys...
Four-Hop Protocol Interactions Van Meter  et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear)  PE EC PC ESC PC A...
The Repeater’s Jobs <ul><li>Entanglement swapping & purification, which require: </li></ul><ul><li>A little bit of quantum...
Entanglement Pumping Ineffective w/ large fidelity difference 0.638 0.638 0.72 0.638 0.75 0.638 0.77 0.638 0.79
Symmetric Purification Problems: Exact matching can  require long waits. Not realistic when memory effects (decoherence)‏ ...
Greedy Purification Doesn’t wait for anything, uses whatever’s available. Works well w/ large number of qubits per repeate...
Banded Purification Large gains in throughput. Moderate # qubits (5-50). Avoids deadlock. Realistic memory model. Simple  ...
Banded Purification Performance Van Meter  et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear), quant-ph:0705.41...
Banded Purification Latency Van Meter  et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear), quant-ph:0705.4128
Protocol Design
Routing Simple: use Dijkstra’s Shortest Path First. ...but we don’t yet know the cost metric. D F A B C E G H
A Different Meaning of  “Which Path?” 3 hops: ACGB 4 hops: ACGHB ACEHB ADEHB ADFHB 5 hops: ACEHGB ADEHGB ADECGB ADFHGB 6 h...
But What is Distance? What if hops are not homogeneous? Are 2 n -1 hops, 2 n   hops, and 2 n +1 hops significantly differe...
How Do We Order These? <ul><li>How does  number  of links matter? </li></ul><ul><li>Does  number  of  weak  links matter? ...
Other Problems <ul><li>Defining swap points </li></ul><ul><li>Static or dynamic? </li></ul><ul><li>Avoiding leapfrog </li>...
Other Problems Partial messaging sequence Can this be made more efficient? Due to memory degradation, gains will be better...
Leapfrog <ul><li>Station 0 </li></ul>Station 1 Station 2 Station 3
Resource Management (QoS?)‏ A<->B & C<->D want to talk. Remember, it’s a  distributed  computation. Worse, fragile quantum...
Open Repeater Problems <ul><li>Well, repeater HW doesn’t work yet... </li></ul><ul><li>Sims of “weak links” mostly functio...
Open Complex Network Problems <ul><li>Coding  partially done </li></ul><ul><ul><li>Using graphviz file format </li></ul></...
Milestones for JSPS <ul><li>Define a cost metric (figure out if it’s additive!) </li></ul><ul><li>Define a path selection ...
Food for Thought <ul><li>When will first  Science  or  Nature  paper appear  using  a quantum computer, but not  about  th...
Thanks <ul><li>Thanks to Thaddeus Ladd, Bill Munro and Kae Nemoto (coauthors on much of this work), as well as Austin Fowl...
AQUA : Advancing Quantum Architecture 情報は物理である: Information is physical http://www.sfc.wide.ad.jp/aqua/
Upcoming SlideShare
Loading in …5
×

PPT

749 views

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
749
On SlideShare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
14
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

PPT

  1. 1. Networking Problems in Using Quantum Repeaters Rodney Van Meter MAUI, 2009/4/16 [email_address] http://www.sfc.keio.ac.jp/~rdv/
  2. 2. Assume a Quantum Computer Like This...
  3. 3. I want to Build a Distributed Quantum System Like This Laboratory-sized quantum multicomputer or transcontinental network, either one!
  4. 4. Repeater Protocol Stack Van Meter et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear), quant-ph:0705.4128 Physical Entanglement (PE)‏ Entanglement Control (EC)‏ Purification Control (PC)‏ Entang. Swapping Ctl (ESC)‏ Purification Control (PC)‏ Application Distance=1 } } Repeated at Different Distances } End-to-End Only quantum!
  5. 5. Outline <ul><li>Two types of quantum networks </li></ul><ul><li>IPsec with QKD </li></ul><ul><ul><li>IPsec with QKD </li></ul></ul><ul><ul><li>US & European efforts </li></ul></ul><ul><ul><li>Open problems & plans </li></ul></ul><ul><li>Repeaters </li></ul><ul><ul><li>Basic concepts </li></ul></ul><ul><ul><li>Our recent results </li></ul></ul><ul><ul><li>Open problems & plans </li></ul></ul>
  6. 6. Two Types of Quantum Networks Unentangled Networks Entangled Networks A B C E G H
  7. 7. Quantum Key Distribution (QKD) <ul><li>Creates a shared, random secret between two nodes </li></ul><ul><li>Uses physical effects to guarantee that key has not been observed </li></ul><ul><li>Requires authenticated classical channel </li></ul><ul><li>Limited to <150km per hop </li></ul>
  8. 8. IPsec with QKD (ORF2008)‏
  9. 9. The DARPA Quantum Network slide from Elliott, BBN
  10. 10. SECOQC Prototype - principle layout Slide from M. Peev, 2008 FOR 81 m LMU
  11. 11. A Trusted repeater QKD-Network: Abstract Architecture (SECOQC, Europe) Slide from M. Peev, 2008 QKD Access Node QKD Core Node Secrets Plane QKD Access Node QKD Core Node VPN-green Site 1 VPN-yellow Site 1 VPN-yellow Site 2 Data Plane Quantum Plane
  12. 12. QKD with IPsec Plans <ul><li>Test over raw fiber, Yagami<->K2 </li></ul><ul><li>Use key for one-time pad </li></ul><ul><li>Work w/ NEC, BBN & ITU to standardize </li></ul><ul><li>Write experimental I-D on IKE changes </li></ul><ul><li>Take to IETF in Hiroshima? </li></ul>
  13. 13. Outline <ul><li>Two types of quantum networks </li></ul><ul><li>IPsec with QKD </li></ul><ul><ul><li>IPsec with QKD </li></ul></ul><ul><ul><li>US & European efforts </li></ul></ul><ul><ul><li>Open problems & plans </li></ul></ul><ul><li>Repeaters </li></ul><ul><ul><li>Basic concepts </li></ul></ul><ul><ul><li>Our recent results </li></ul></ul><ul><ul><li>Open problems & plans </li></ul></ul>A B C E G H
  14. 14. Network Link Technology (Qubus)‏ coherent optical source (laser)‏ waveguide homodyne detector transceiver qubit in node 1 transceiver qubit in node 2 millimeters to kilometers Munro, Nemoto, Spiller, New J. Phys. 7, 137 (2005)‏ Ladd et al., NJP 8, 184 (2006)‏
  15. 15. Quantum Repeater Operation: Entanglement Swapping Station 0 Station 1 Station 2 Bell State Measurement Fidelity decreases; you must purify afterwards Results must be communicated
  16. 16. Nested Entanglement Swapping
  17. 17. Purification Station 0 Station 2 Results must be communicated (two-way?)
  18. 18. Repeater Protocol Stack Van Meter et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear), quant-ph:0705.4128 Physical Entanglement (PE)‏ Entanglement Control (EC)‏ Purification Control (PC)‏ Entang. Swapping Ctl (ESC)‏ Purification Control (PC)‏ Application Distance=1 } } Repeated at Different Distances } End-to-End Only quantum!
  19. 19. Four-Hop Protocol Interactions Van Meter et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear) PE EC PC ESC PC App ESC PC PE EC PC ESC PC App ESC PC PE EC PC ESC PC ESC PE EC PC ESC PE EC PC ESC
  20. 20. The Repeater’s Jobs <ul><li>Entanglement swapping & purification, which require: </li></ul><ul><li>A little bit of quantum communication </li></ul><ul><li>Quantum memory </li></ul><ul><li>Local quantum operations (gates & measurements) </li></ul><ul><li>Lots of decision making (both local and distributed) </li></ul><ul><li>Lots of classical communication </li></ul>
  21. 21. Entanglement Pumping Ineffective w/ large fidelity difference 0.638 0.638 0.72 0.638 0.75 0.638 0.77 0.638 0.79
  22. 22. Symmetric Purification Problems: Exact matching can require long waits. Not realistic when memory effects (decoherence)‏ considered. Can deadlock if resources are limited. 0.638 0.638 0.72 0.638 0.638 0.797 X 0.72
  23. 23. Greedy Purification Doesn’t wait for anything, uses whatever’s available. Works well w/ large number of qubits per repeater. 0.638 0.638 0.72 0.638 0.638 0.757 X
  24. 24. Banded Purification Large gains in throughput. Moderate # qubits (5-50). Avoids deadlock. Realistic memory model. Simple to implement in real time (even in HW). Probably not optimal, but probably close. 0.638 0.638 0.72 0.638 0.638 0.797 X 0.72 Divide fidelity space into multiple bands e.g., above & below 0.70
  25. 25. Banded Purification Performance Van Meter et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear), quant-ph:0705.4128
  26. 26. Banded Purification Latency Van Meter et al. , IEEE/ACM Trans. on Networking, Aug. 2009 (to appear), quant-ph:0705.4128
  27. 27. Protocol Design
  28. 28. Routing Simple: use Dijkstra’s Shortest Path First. ...but we don’t yet know the cost metric. D F A B C E G H
  29. 29. A Different Meaning of “Which Path?” 3 hops: ACGB 4 hops: ACGHB ACEHB ADEHB ADFHB 5 hops: ACEHGB ADEHGB ADECGB ADFHGB 6 hops: ACECGHB 7 hops: ADFHECGB ACEDCHGB A B C D E F G H
  30. 30. But What is Distance? What if hops are not homogeneous? Are 2 n -1 hops, 2 n hops, and 2 n +1 hops significantly different? A B C D E F G H
  31. 31. How Do We Order These? <ul><li>How does number of links matter? </li></ul><ul><li>Does number of weak links matter? </li></ul><ul><li>Does position of weak link matter? </li></ul><ul><li>Is cost additive? </li></ul><ul><li>At this logical level, is this technology-independent? </li></ul>
  32. 32. Other Problems <ul><li>Defining swap points </li></ul><ul><li>Static or dynamic? </li></ul><ul><li>Avoiding leapfrog </li></ul><ul><li>Avoiding deadlock </li></ul><ul><li>Minimizing waits for classical messages </li></ul>
  33. 33. Other Problems Partial messaging sequence Can this be made more efficient? Due to memory degradation, gains will be better than linear
  34. 34. Leapfrog <ul><li>Station 0 </li></ul>Station 1 Station 2 Station 3
  35. 35. Resource Management (QoS?)‏ A<->B & C<->D want to talk. Remember, it’s a distributed computation. Worse, fragile quantum memory means there is a hard real time component. ==>requires circuit switching ??? (bottleneck likely is memory per node)‏ A B C D
  36. 36. Open Repeater Problems <ul><li>Well, repeater HW doesn’t work yet... </li></ul><ul><li>Sims of “weak links” mostly functional </li></ul><ul><li>Establishing swapping points </li></ul><ul><li>More dynamic behavior </li></ul><ul><li>Non-power-of-two hops </li></ul><ul><li>Finish & publish protocol state machine </li></ul>
  37. 37. Open Complex Network Problems <ul><li>Coding partially done </li></ul><ul><ul><li>Using graphviz file format </li></ul></ul><ul><ul><li>Routing not done </li></ul></ul><ul><ul><li>Workload generator needs work </li></ul></ul><ul><ul><li>QoS / resource allocation not implemented </li></ul></ul><ul><li>Visualization of networks </li></ul><ul><li>Investigate graph states & quantum network coding </li></ul><ul><li>More detailed workload definition </li></ul>
  38. 38. Milestones for JSPS <ul><li>Define a cost metric (figure out if it’s additive!) </li></ul><ul><li>Define a path selection algorithm </li></ul><ul><li>Define test cases </li></ul><ul><li>Simulate that set of test cases </li></ul><ul><li>Extend to topologically complex networks </li></ul><ul><li>Create static visualizations </li></ul>
  39. 39. Food for Thought <ul><li>When will first Science or Nature paper appear using a quantum computer, but not about the quantum computer? </li></ul><ul><li>That is, when will a quantum computer do science, rather than be science? </li></ul><ul><li>Answers from quantum researchers range from “less than five years” to “more than forty years” </li></ul>
  40. 40. Thanks <ul><li>Thanks to Thaddeus Ladd, Bill Munro and Kae Nemoto (coauthors on much of this work), as well as Austin Fowler, Jim Harrington, Kohei Itoh, Agung Trisetyarso, Byung-Soo Choi, Shota Nagayama, and Takahiko Satoh </li></ul><ul><li>And funding from NICT, MEXT, NSF, the Mori Fund at Keio, and now JSPS for funding. </li></ul>Copyright © 2006 Keio University  |  
  41. 41. AQUA : Advancing Quantum Architecture 情報は物理である: Information is physical http://www.sfc.wide.ad.jp/aqua/

×