The Arrival of Quantum Computing – Quantum Networks
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This document discusses the current advancements and applications of quantum computing and communication, highlighting significant technologies such as quantum key distribution and the hardware required for these applications, including superconducting circuits and silicon quantum dots. It details the potential of quantum internet technology for secure communication and parallelized computation, while outlining challenges like scalability using current wiring technologies. The research also acknowledges collaborations and developments in electro-optic conversion for improving the efficiency of quantum technologies.
The Arrival of Quantum Computing – Quantum Networks
- 1. The Arrival of Quantum Computing Jeremy Witmer Phd. Candidate at Stanford University, Applied Sciences
- 2. Jeremy Witmer Stanford University Quantum networks Jeremy Witmer Stanford University Impact Seminar 2018-04-19 Laboratory for Integrated Nano-Quantum Systems
- 3. Jeremy Witmer Stanford University Quantum technologies Quantum Computing Applications: • Code breaking (Shor’s algorithm) • Quantum simulation (chemistry, materials, drug discovery) • Machine learning Hardware: • Superconducting circuits • Trapped ions • Silicon quantum dots • Many others… Quantum Communication Applications: • Secure communication (quantum key distribution) • Quantum internet Hardware: • Light in optical fiber • Light in free-space Quantum Sensing Applications: • Gravitometry (geo-surveying) • Magnetometry (materials science, MRI) Hardware: • Atomic clocks • NV centers in diamond Our research
- 5. Jeremy Witmer Stanford University Quantum communication in the news
- 6. Jeremy Witmer Stanford University What is quantum key distribution? • “One-time pad” • Share secret key ahead of time (random string of bits, as long as message). • To encrypt message, XOR it with key. Decrypt is the same. • Impossible to decrypt, information is completely scrambled. • Question: How to share secret key? • Idea: Transmit the secret key using single photons. Allows eavesdroppers can be detected! • Potential for perfectly encrypted communication. (But still need to design system carefully)
- 7. Jeremy Witmer Stanford University Quantum communication: major players • DARPA (Boston) • Los Alamos National Lab • Tokyo • Geneva • Beijing-Shanghai fiber link • China quantum satellite Government-sponsored QKD networks: Geneva New YorkCanberra Quantum key distribution companies: Newer companies: • SeQure Net (France) • Infiniquant (Germany) • KETS Quantum Security (UK) • QuNu Labs (India) Notes: • Chinese government is hugely invested (~ $2 billion) • Nothing in Silicon Valley (that I know of)
- 8. Jeremy Witmer Stanford University Quantum technologies Quantum Computing Applications: • Code breaking (Shor’s algorithm) • Quantum simulation (chemistry, materials, drug discovery) • Machine learning Hardware: • Superconducting circuits • Trapped ions • Silicon quantum dots • Many others… Quantum Communication Applications: • Secure communication (quantum key distribution) • Quantum internet Hardware: • Light in optical fiber • Light in free-space Quantum Sensing Applications: • Gravitometry (geo-surveying) • Magnetometry (materials science, MRI) Hardware: • Atomic clocks • NV centers Our research
- 9. Jeremy Witmer Stanford University Why a quantum internet? 1. Allows for parallelized computation. (Computational power scales exponentially with number of processors.) 1. Scaling superconducting quantum processors beyond ~ 1000 qubits impossible with current RF cables. Optical communication provides an alternative. 1. Enables quantum-secured private communication over long distances.
- 10. Jeremy Witmer Stanford University Courtesy of IEEE Spectrum, Google Google Quantum Computing Quantum CommunicationPhotons in optical fibers How can we connect these? Superconducting qubits
- 11. Jeremy Witmer Stanford University The backbone of the (classical) internet Electro-optic modulators Electro-optic effect: n: refractive index E: electric field r: electro-optic coefficient Light in Signal electro-optic Modulated light out V + - 1 0
- 12. Jeremy Witmer Stanford University electro-optic L C Microwave input/output Optical fiber input/output Electro-optic conversion Mirrors Resonant LC circuit Qubit processor
- 13. Jeremy Witmer Stanford University Electro-optic converter design Grating (light input) Photo nic crystal mirror Optical resonator Capaci tor Photonic crystal mirror 2 um Grating 10 um Overview 1 mm
- 14. Jeremy Witmer Stanford University Our hardware Dilution refrigerator Converter chip Optical IO Microwave IO
- 15. Jeremy Witmer Stanford University Cryogenic microwave-to-optical conversion Optical power measurement Our first converted photons! Current conversion efficiency is low (<< 1%), but we have ideas to improve it.
- 16. Jeremy Witmer Stanford University Quantum technologies Quantum Computing Applications: • Code breaking (Shor’s algorithm) • Quantum simulation (chemistry, materials, drug discovery) • Machine learning Hardware: • Superconducting circuits • Trapped ions • Silicon quantum dots • Many others… Quantum Communication Applications: • Secure communication (quantum key distribution) • Quantum internet Hardware: • Light in optical fiber • Light in free-space Quantum Sensing Applications: • Gravitometry (geo-surveying) • Magnetometry (materials science, MRI) Hardware: • Atomic clocks • NV centers Our research
- 17. Jeremy Witmer Stanford University Acknowledgements Laboratory for Integrated Nano-Quantum Systems Stanford Graduate Fellowship Stanford Nanofabrication Facility & Stanford Nano Shared Facitilities Collaborators: Prof. Jingdong Luo Prof. Alex Jen Francis Lin (U Washington, City U Hong Kong) Timothy McKenna Raphael Van Laer Patricio Arrangoiz-Arriola Prof. Amir Safavi-Naeini
- 18. Jeremy Witmer Stanford University Extra slides
- 19. Jeremy Witmer Stanford University Conclusions • Electro-optic effect allows us to convert light and microwaves directly • Make converter chip using electro-optic polymer and silicon photonics • Demonstrated microwave-to-optical signal conversion in dilution refrigerator
- 20. Jeremy Witmer Stanford University What is “quantum key distribution”? Provably secure (unbreakable) assuming the following three conditions: • The key is completely random • The key is as long as the message • The key is never reused Plain-text 1 1 1 0 1 0 1 0 1 0 1 0 0 1 0 0 0 1 0 0 1 1 1 0 XOR Alice Bob Secret key Cypher-text One-time pad encryption
- 21. Jeremy Witmer Stanford University Silicon photonics with electro-optic polymers EO polymer properties: • Highly polar chromophore molecule embedded in host polymer • Large electro-optic coefficients: EO polymers: > 400 pm/V (Lithium niobate: 31 pm/V) • Spin coat as final cladding layer → simplifies fabrication • Low optical loss (can be < 1 dB/cm) • Low MW loss (not piezo-electric!) • Must be poled in-device +-
- 22. Jeremy Witmer Stanford University Two operating modes Pump on low-frequency side: Converts microwave photon to optical photon Pump on high-frequency side: Creates entangled microwave and optical photons Freq. pump … Freq. pump …
- 23. Jeremy Witmer Stanford University Next step: high-L spiral inductors Grating coupler Photonic crystal mirror Optical cavity Capacitor High-Z0 spiral inductor High-Z0 spiral inductor 20 um Airbridge process 2 um
- 24. Jeremy Witmer Stanford University Scaling superconducting quantum computers Courtesy of IEEE Spectrum, Google IBM
- 25. Jeremy Witmer Stanford University Connecting quantum computers mm waves? M. Pechal et al, Phys. Rev. A 96, 042305 (2017) Solution: use light!
- 26. Jeremy Witmer Stanford University Microwave-to-optical different approaches Electro-optics: Schwefel, Painter and Leuchs groups, 2016 Optomechanics: Cleland group, U Chicago, 2016 Also Srivinavasan group, NISTLehnert and Regal groups, CU Boulder, 2014 Magnonics: Nakamura group, Tokyo, 2016 Spin systems: Faraon group, Caltech, 2017