quantum computer building blocks
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Quantum Computer Building Blocks . Paola Cappellaro Quantum Engineering Group - MIT. The approach to QIP. Challenges in quantum information Engineer a scalable quantum system Control a large quantum system… …before decoherence ruins it Bottom-up approach - PowerPoint PPT PresentationTRANSCRIPT
Quantum ComputerBuilding Blocks
Paola CappellaroQuantum Engineering Group - MIT
P. Cappellaro —
The approach to QIP
• Challenges in quantum information– Engineer a scalable quantum system– Control a large quantum system…– …before decoherence ruins it
• Bottom-up approach1. Use small quantum building blocks2. Perfect their control3. Combine them in a modular way
P. Cappellaro —
Distributed quantum computing• Modular, hybrid architecture for quantum computing
1. quantum registers for simple algorithms and local memory2. quantum actuators to interface the registers with the
classical controllers 3. quantum wires to connect the registers
P. Cappellaro —
ELECTRON-NUCLEAR SPINQUANTUM REGISTERS
P. Cappellaro —
• Electronic spin surrounded by nuclear spins• Hyperfine interaction creates a local field Bhyp
– Close-by nuclei quantized in Bhyp dephasing
– Farther away nuclei create a fluctuating field: electron spin decoherence
Bhyp
Quantum registers
Closest nuclei have distinct frequency qubits
P. Cappellaro —
• Isolated electronic spin– From 2 unpaired electrons Spin 1
• Optically active– Single electronic spin observed by fluorescence
Nitrogen-Vacancy (NV) centers
Confocal Microscope
P. Cappellaro —
NV centers: optical control
• Spin-selective fluorescence– Spin state read-out
Fluorescence
P. Cappellaro —
NV centers: optical control
• Spin-selective fluorescence– Spin state read-out
Fluorescence
P. Cappellaro —
NV centers: optical control
• Spin-selective fluorescence– Spin state read-out
200 ns
Fluorescence
P. Cappellaro —
NV centers: optical control
• Spin-selective fluorescence– Initialization to ground
state
Effective T ~ mK
at room temperature!
3A2
1A1
3E
P. Cappellaro —
• Optical initialization & readout• Ground state– Control via ESR– Effective qubit
• Complex spin environment– Nuclear spins: N,13C– Epr impurities (nitrogens)
• Close-by nuclear spins quantum register
NV centers: spin control
P. Cappellaro —
ACTUATOR CONTROL
P. Cappellaro —
• Quantum register– Electronic qubit for initialization and communication – Nuclear qubits for memory and error correction
• Only need 2 types of logic gates:
1) Single qubit gate 2) Controlled gate on electronic spin on nuclear spins
• All other gates can be built from these two
Gates for quantum registers
P. Cappellaro —
• Use electron as an actuator– Inducing nuclear rotation about 2 axis
– Can obtain universalcontrol
– Need strong anisotropy– In ms=1, faster
rotation than rf pulse– Good isolation of the registers
Electronic spin-only Control
ms=0 ms=1
Electron pulse
P. Cappellaro —
Advanced techniques• Addressing individual nuclei with rf field– Limits on nuclear Rabi frequency long pulse
times– Off-resonance modulation, pulse errors, spin
couplings, …• Tools– Composite pulses– Numerically optimized pulses
r.f. p
ower
t
AWG
MW Signal source
IQ
Pulse Blaster
50Ω
Power detector
Oscilloscope
Spectrum analyzer
Directional Coupler
SwitchIQ Mixer
Pre-AmpAmplifier Circulator Load
50ΩMixer
RF Control Line
Sample
rf-Switch rf-Amplifier rf -Circulator Load
Pre-Amp
Filter
Filter
Microwave Control Setup
P. Cappellaro —
Clarice Aiello
Masashi Hirose
Ashok Ajoy Honam Yum
Alex Cooper
Gurneet Kaur
Thanks!
MartinGoycoolea
Jonathan Schneider
Gary Wolcowitz
P. Cappellaro —
Funding
AFOSR YIPNSF CUAxQIT (Keck Foundation)
Publications F. Ticozzi, R. Lucchese, P. Cappellaro, L. Viola, "Hamiltonian Control of Quantum Dynamical Semigroups: Stabilization and Convergence Speed" To appear in IEEE Transaction on Automatic Control, arXiv:1101.2452