1. A Link Layer Protocol for Quantum Networks
Axel Dahlberg, Matt Skrzypczyk, Tim Coopmans, Leon Wubben, Filip Rozpędek, Matteo Pompili, Arian Stolk, Przemysław Pawełczak, Robert Knegjens, Julio de Oliveira Filho, Ronald Hanson, Stephanie Wehner
ACM SIGCOMM 2019 – Wednesday 08/21/2019

2. Joint work with Axel Dahlberg Tim Coopmans Leon Wubben Filip Rozpędek
Matteo Pompili
Arian Stolk
Przemysław Pawełczak
Rob Knegjens
Julio de Oliveira Filho
Ronald Hanson
Stephanie Wehner

3. Quantum Information
Classical
Quantum 1
0+1

4. Applications Quantum Key Distribution Clock Synchronization
Bennett and Brassard. Theor. Comput. Sci (2014): 1984
Ekert. Physical review letters 67.6 (1991):
Clock Synchronization
Gottesman, Jennewein, and Croke. Physical Review Letters (2012)
Secure Quantum Computing in the Cloud
Fitzsimons and Kashefi. Physical Review A 96.1 (2017). 2017

5. Quantum Network Structure
End Node
Bridge long
distances
Repeater
Prepare/Measure Qubits
Store/Manipulate Qubits

6. Stages of Quantum Networks
Functionality
Quantum Computing Networks
Cryptography
Sensing and Metrology
Distributed Systems
Secure Quantum Cloud Computing
Fault-Tolerant Few Qubit Networks
Quantum Memory Networks
Entanglement Distribution Networks
Prepare and Measure Networks
Trusted Repeater Networks
Time
Wehner, Elkouss, and Hanson. Science 362, 6412 (oct)

7. Our Contribution Functional allocation of quantum network stack
Systematic study of design considerations and use cases
First physical and link layer protocols
Performance evaluation and scheduling investigation

8. Related Work Entanglement generation experiments QKD networks
Hensen et al. Nature 526, 7575 (2015),
Hofmann et al. Science 337, 6090 (2012),
QKD networks
Liu et al. ACM SIGCOMM Computer Communication Review. Vol. 43. No
Yu et al. IEEE International Conference on Computer and Communications. IEEE, 2017
Network stack sketches
Aparicio et al. Asian Internet Engineering Conference. ACM, 2011
Pirker and Dür. New Journal of Physics

9. Why a Quantum Network Stack is Different
No copying! Short lifetime!
Inherently connected!

10. Sending Qubits via Entanglement
End node
End node

11. Sending Qubits via Entanglement
End node
End node

12. Sending Qubits via Entanglement
End node
End node

13. Quantum Repeater… Entanglement Swapping
End node
Repeater
End node

14. Quantum Repeater… Entanglement Swapping
End node
Repeater
End node

15. Quantum Repeater… Entanglement Swapping
End node
Repeater
End node

16. Example of Quantum Hardware
Nitrogen vacancy in diamond
Communication qubit
Storage qubits
Entanglement at 1.3 km
10 mm

17. Physical Entanglement Generation

18. How Entanglement is Produced

19. Our Contribution Functional allocation of quantum network stack
Systematic study of design considerations and use cases
First physical and link layer protocols
Performance evaluation and scheduling investigation

20. Quantum Network Stack
Application
Transport
Network
Link
Physical

21. Quantum Network Stack Application Transport Network Link Physical
Quantum Application Protocols
Transport
End-to-end Qubit Delivery
Network
Long-distance Entanglement Generation
Link
Entanglement Generation on a Link
Physical
Quantum Device Layer

22. Quantum Network Stack Application Transport Network Link Physical
Quantum Application Protocols
Transport
End-to-end Qubit Delivery
Network
Long-distance Entanglement Generation
Link
Entanglement Generation on a Link
Physical
Quantum Device Layer

23. Our Contribution Functional allocation of quantum network stack
Systematic study of design considerations and use cases
First physical and link layer protocols
Performance evaluation and scheduling investigation

24. Link Layer: Entanglement Generation Service
CREATE
OK, …
OK, …
QEGP
QEGP

25. Performance Metrics Quantum Metrics
Fidelity: quality of entanglement, rate of success trade-off
Standard Metrics
Latency: issuing request to getting a pair
Throughput: pairs/s
Fairness: difference in performance metrics between nodes

26. Use Cases Application Use Cases
Measure directly: many pairs measured immediately
Create and keep: few pair(s) stored for processing
Network Layer Use Case
Create and keep: entanglement swapping with two pairs

27. Design Considerations
Noise due to attempts
Producing entanglement induces noise on storage qubits
(Kalb et al, Phys. Rev. A, )
Avoid triggering unless both nodes agree
Noise is time dependent
Avoid waiting once entanglement made
Prior discussion preferred
Quantum CRC for error detection difficult
Applications do not require perfect entanglement
Reduce complexity

28. Our Contribution Functional allocation of quantum network stack
Systematic study of design considerations and use cases
First physical and link layer protocols
Performance evaluation and scheduling investigation

29. CREATE: Expected Service
Node A
Node B
QEGP
QEGP
Link Layer
Physical Layer
Higher layer to QEGP
Remote node ID, # pairs, min fidelity, max time, request type, ...

30. OK: Expected Service QEGP to higher layer
Node A
Node B
QEGP
QEGP
Link Layer
Physical Layer
QEGP to higher layer
Entanglement ID, qubit ID, fidelity estimate, ...

31. A Link Layer Protocol

32. A Link Layer Protocol

33. A Link Layer Protocol

34. A Link Layer Protocol

35. A Link Layer Protocol

36. A Link Layer Protocol

37. A Link Layer Protocol

38. A Link Layer Protocol

39. A Link Layer Protocol

40. A Link Layer Protocol

41. A Link Layer Protocol

42. A Link Layer Protocol

43. A Link Layer Protocol

44. A Link Layer Protocol ?

45. How to Prioritize CREATE Requests
Requires context and information
Simple version: first come first serve
More interesting: cater to different use cases

46. Our Contribution Functional allocation of quantum network stack
Systematic study of design considerations and use cases
First physical and link layer protocols
Performance evaluation and scheduling investigation

47. Simulation Tool: NetSQUID
Discrete event simulator
Model and validate simulated quantum hardware
Model physical components e.g. fibers, nodes, and midpoint

48. Simulation Environment: SurfSARA
Long runs
Protocol robustness: recovery mechanisms
Short runs
Performance trade-offs: latency, throughput and fidelity
Metric fluctuations: different scheduling strategies
Simulations
Core hours
Simulated time
Scenarios
2578
94244
707 hours
173

49. Simulation Example: QL2020
KPN PB400
node location
15km
KPN PBX
detector location
Assumed loss
0.1 dB/splice
0.3 dB/km
10km
TU Delft
node location

50. Evaluation: Quantum Hardware Model
Simulate experiments
Fidelity vs rate of success
Qubit memory lifetimes

51. Evaluation: Single Request Types
Parameters
Takeaways
Robust against extreme channel loss
Fidelity primarily impacts latency and throughput
Request frequency
0.9
Fidelity
>0.5
Control message loss
probability
Up to 10^-4

52. Some Takeaways Protocol robust Fidelity versus throughput and latency
Mixed request simulations
Scheduling versus performance metrics

53. Our Contribution Functional allocation of quantum network stack
Systematic study of design considerations and use cases
First physical and link layer protocols
Performance evaluation and scheduling investigation

54. Future Work Hardware realization of Link Layer (ongoing)
Network Layer Protocol
Other (smarter) scheduling strategies
Combat memory lifetimes
Consider role of node in network

55. Thank you