1 / 34

Wiring up a Quantum Computer

Wiring up a Quantum Computer. Paola Cappellaro Quantum Engineering Group - MIT. Distributed quantum computing. M odular , hybrid architecture for quantum computing quantum registers for simple algorithms and local memory. quantum wires to connect the registers.

monita
Download Presentation

Wiring up a Quantum Computer

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Wiring up a Quantum Computer Paola CappellaroQuantum Engineering Group - MIT

  2. Distributed quantum computing • Modular, hybrid architecture for quantum computing • quantum registers for simple algorithms and local memory • quantum wires to connect the registers

  3. Quantum Information Transport

  4. I-mode at Alcator C-mod: Turbulent-Transport In High-Performance, ITER Relevant Plasmas (A. White) Strain Coupling to the Reactivity and Transport Properties of Solid Oxide Fuel Cell Materials (B. Yildiz) Beyond Multigroup: An Alternative for the Energy Treatment in Radiation Transport (B. Forget) Quantum Information Transport

  5. State-Transfer in spin chains • Flip-flops transport a single-spin excitation |0 0 0 0 0 0 0 0〉 • Similar to spin-waves driven by Heisenberg exchange Hamiltonian • Most common model is the xx-Hamiltonian 1 1

  6. Optimal Transport • Perfect transport for F Spin # 5 10 15 20

  7. Optimal Transport • Perfect transport for F Spin N Spin 1 Time

  8. Dispersive Transport • Limited fidelity for F Spin # 5 10 15 20

  9. Dispersive Transport • Limited fidelity for F Spin 1 Spin N Time

  10. Transport Fidelity Optimal couplings Equal couplings A. Ajoy, P. Cappellaro, to appear in Phys. Rev A

  11. ImplementationsNuclear spins in apatite crystalsElectronic spins in diamond Nuclear spins in apatite crystals

  12. Simulation with NMR • Nuclear spins in regular crystal • Advantages: • Well-defined geometry • Good control • Long coherence times • Challenges: • No single-spin addressability

  13. FluorApatite • Single-crystal, Ca5F(PO4)3 • Quasi-1D system: • Ratio of couplings: Cin/Cx= Dx3/din340 Bz 19F spin ½ • Generate the transport interaction • Prepare the initial state

  14. Create Transport Hamiltonian • xx-Hamiltonian usually is not available • Use coherent control to create (on average) the transport Hamiltonian • Constraints on control (collective rotations) • DQ-Hamiltonian simulates transport

  15. Create DQ-Hamiltonian • Rotate the natural dipolar interaction • On average we obtain z 2t t/2 t/2 x y

  16. Create DQ-Hamiltonian • More complex sequence ➙better approximation

  17. Create Initial State • Initial state: thermal state, • Leave just one spin polarized: • Spin 1 has just 1 neighbor ➙different evolution Px x-polarization: t*

  18. Chain Ends Selection • Simple control scheme • Similar scheme for readout of end-chain spins • NMR spectrum of the two initial states

  19. Transport • Compare dynamics of Thermal vs. End Chain E/E T/T E/T T/E

  20. Transport • Compare dynamics of Thermal vs. End Chain E/E T/T E/T T/E G. Kaur, P. Cappellaro, arXiv:1112.0459

  21. Outlook • Investigate deviations from ideal behavior • and devise methods to still achieve transport. • Full control of chain end spins in FAp with high proton defect density • Universal control of the entire chain • Direct readout of transport • New playground for non-equilibrium many-body physics and simulation

  22. ImplementationsNuclear spins in apatite crystalsElectronic spins in diamond Electronic spins in diamond

  23. Nitrogen spin chains • Precise implantation of nitrogens in diamond • Some are converted to NV • Leftovers nitrogen impurities • NV addressed optically • sub-diffraction limit • Nitrogen spins act as spin-chain wires P.Spinicelli et al., New J. Phys. 13, 025014(2011)

  24. Nitrogen spin chains • Challenges • Implantation is not precise enough • Study transport in complex 3D networks • NV spins are still too close-by for confocal microscopy • Use (1) sub-diffraction-limit (STED) techniques to address them, combined with (2) microwave control.

  25. Complex Networks • Randomly distributed spins in a lattice • Distance-dependent interactions • Network represented by adjacency matrix

  26. Weak Coupling • Couple the end-spins only very weakly: • Information is slowly transported from 1 ➙ N irrespective of details in the fast bulk dynamics

  27. Speed vs. Fidelity • Transport in ANY network, but compromise: • Setting the end-spins on resonance with a collective bulk mode increases the speed • Off-resonance condition yields higher fidelity 25 nitrogens (1ppm), ~40nm

  28. High spatial resolution • Optical control with STED techniques: • Donut beam switches off signal from other spins • Increase the spatial resolution to ~10nm • … more complex setup

  29. Higher spatial resolution • Nano-scale magnetic field control • Fabrication of small circuit to create • Static magnetic fields and gradients • High-power microwave/radiofrequency fields

  30. Conclusions • A different type of transport • Quantum wires are a key ingredients for a distributed, scalable quantum computer • Spin chains and networks can be used as wires to transport quantum information • Perfect transport conditions • Experimental implementations

  31. Funding NSF DMR MISTI AFOSR YIP Publications A. Ajoy and P. Cappellaro, "Mixed-state quantum transport in correlated spin networks” Phys. Rev. A 85, 042305 (2012) G. Kaur and P. Cappellaro, "Initialization and Readout of Spin Chains for Quantum Information Transport" arXiv:1112.0459 (To appear in New J. of Phys.) C. Ramanathan, P. Cappellaro, L. Viola and D.G. Cory, "Experimental characterization of coherent magnetization transport in a one-dimensional spin system” New J. Phys. 13 103015 (2011) P. Cappellaro, L. Viola, C. Ramanathan, "Coherent state transfer via highly mixed quantum spin chains” Phys. Rev. A 83, 032304 (2011)

  32. Alex Cooper Gary Wolcowitz Clarice Aiello Masashi Hirose Thanks! Honam Yum Ashok Ajoy GurneetKaur Jonathan Schneider Martin Goycoolea

More Related