Silicon Quantum Computing. David Williams

Transcription

1 Silicon Quantum Computing David Williams Hitachi Cambridge Laboratory, Hitachi Europe Ltd HVM MNT Expo 2006

2 Hitachi s R&D Organization President Mr. K. Furukawa R&D Group Dr. J. Kawakami Sr. Vice President and Head of R&D Group Central Research Laboratory Advanced Research Laboratory Hitachi Research Laboratory System Development Laboratory Mechanical Engineering Research Laboratory Production Engineering Research Laboratory Information, Communication, Multimedia, Electronic Devices, Life Sciences Advanced / Fundamental Research Materials & Basic Technologies, Devices & Components, Social Systems Service Solutions, Information Networks, Software Mechatronics Production Systems, Production Processes & Facilities Global R&D Design Division Intellectual Property Group Business Group Development Laboratory/Division Business Division Development Center Development/Design

3 R&D Labs in Europe Corporate Technology Group, Hitachi Europe Ltd. Hitachi Cambridge Laboratory Hitachi Dublin Laboratory - Fundamental Device Physics - 11 staffs - Numerical Analysis - 6 staffs Headquarters Automotive R&D Laboratory Dublin - Automotive Systems - 4 staffs Cambridge - R&D Maidenhead Management - 5 staffs Pari s Sophia Antipolis Hitachi Sophia Antipolis Laboratory - Mobile Communication and Security - 9 staffs (HEU/CTG) Munich Milan Hitachi Design Centre Europe - Industrial Design and Service Solutions - 4 staffs

4 Quantum Information Group Hitachi Cambridge Laboratory, Hitachi Europe Ltd. Microelectronics Research Centre, Cambridge University Xiulai Xu Dave Williams Luke Robinson Mike Tanner Nick Stone Leonor Sierra Jas Sandhu Jon Mar Mohammed Khalid Greg Hutchinson David Hasko Kiyotaka Hammura John Gorman Lisa Cresswell Richard Collier John Cleaver Paul Chapman Andrey Bychkov Adel Bririd Barney Balmforth Hugh Baker Aleksey Andreev

5 Silicon device trends How we think about the transistors now A 25 nm MOSFET In production 2008 A 4.2 nm MOSFET In production??? Asen Asenov, Glasgow IEEE Trans Electron Dev 50(9), 1837 (2003)

6 CMOS logic is holding on It s not good enough to be slightly better than conventional silicon circuitry To be useful, new electronic devices must perform new functions or vastly outperform silicon ULSI

7 Generations of Information Processing Turing / von Neumann: Universal Machine 1940s We can make computers Landauer and others: Information is Physical 1970s Computers need cooling fans Deutch: Physical Information is Quantum 1980s Computers get weird

8 Quantum Information Processing (QIP) Quantum Cryptography Quantum Computation The principle of quantum mechanics guarantees absolute security of communication Massive parallelism of quantum entanglement is used for computational goals Can be used for distributing classical cryptographic keys in a completely secure way A totally new way of processing information: A single quantum computer can solve some problems that all the conventional computers in the world cannot MANIPULATION Eve READ OUT Alice Quantum information Bob QUBIT INITIALIZATION Semiconductor qubit We want to find solid-state implementations

9 The Quantum Bit - qubit Qubit - a quantum two-level system: represent as a vector on a Bloch sphere: infinite choice of state z 0> Qubit y x 1/ 2 ( 0> + 1>) Measurement yields 0> or 1> only Why? If we entangle multiple qubits, the computational power increases exponentially with the number of qubits, so we can potentially perform computations impossible by other means When? The break point is ~ 100 perfect qubits ~1,000-10,000 with error correction (Steane)* *Requires switching:coherence ratio~ 1:104 How? Solid-state qubits Nielsen and Chuang Quantum Computation and Quantum Information CUP (2000)

10 Requirements for good qubits 1. The ability to define a set of two-level quantum systems 2. The ability to prepare them in a known state 3. The opportunity for them to evolve without decoherence 4. Known (and possibly controllable) interactions between them 5. The ability to measure their state after computation

11 Qubit devices Methods of manipulation: DC High frequency: Continuous wave Pulsed

12 Qubit devices Methods of manipulation: DC High frequency: Continuous wave Pulsed MANIPULATION READ OUT QUBIT INITIALIZATION

13 Silicon Qubit Long coherence time (200ns vs 2ns) Acoustic isolation Non-polar phonons Standard processing techniques Easily scalable to 2-D arrays

14 Scaling and Control We need to integrate the qubits to make quantum gates, with controlled qubit-qubit interactions, state initialisation, control during processing, and readout. Quantum Computing with Globally Controlled Exchange-type Interactions Simon Benjamin Quant-phy/

15 Cryogenic Instrumentation for Quantum Electronics Qubit nanostructure Cryogenic CMOS Custom circuit RT CMOS RT 4.2K mk OXFORD UNIVERSITY