Modeling Read-Out for Solid-State Quantum Computers in Silicon Vincent Conrad Supervisors: C.Pakes & L. Hollenberg

Introduction Solid-State Quantum Computers in Silicon Modeling Read-Out Results & Conclusion Further Work Single Electron Transistors

Hard QubitsScalable Solid-State Quantum Computers in Silicon Kane Quantum Computer Buried Donor Charge Qubit Quantum Computer Spin-Qubit Charge-Qubit

Kane Quantum Computer

spin-qubit

Buried Donor Charge-Qubit Quantum Computer Charge-qubit

Single Electron Tunneling Energy spacing must be greater then thermal smearing Quantised energy levels Potential Barriers { Fermi Level of Source is lower then first unoccupied level of dot

Single Electron Tunneling Applying a potential shifts the dot’s energy levels. Fermi energy of source now higher then dot’s 1 st unoccupied energy level. An electron can now occupy the dot. Coulomb blockade prevents others.

Single-Electron Transistor Including a control gate allows us to manipulate the island’s energy levels. source drain dot (island) control controlled single electron tunneling S E T

Orthodox SET theory The only quantized energy levels occur in the island. The time of electron tunneling through the barrier is assumed to be negligibly small. Coherent quantum processes consisting of several simultaneous tunneling events ("co-tunneling") are ignored. Energy stored in a capacitorWork done by tunneling events

SET Sensitivity conductance control gate voltage electron motion extremely sensitive to voltage variations on the island

Read-Out Single electron’s motion between dopants. Induced island charge. Vary potential on the island (control gate). Require induced charge > SET sensitivity. drain islandsource electron hole

Spin-Qubit Read-Out Q = CV

Charge Qubit Read-Out Q = CV

Results N.B. For charge qubit  q is difference between two points. = 2.49x10 -2 e= 2.14x10 -2 e

Conclusions Induced island charge >> SET Sensitivity Need an answer before information loss Electron-spin relaxation time (spin-qubit) Charge dissipation time (charge-qubit) Time given by shot-noise limit Well inside estimated times for both information loss mechanisms Both qubit types should produce measurable results using current technology made by the SRCQCT 2 x e >> 3.2 x e

Further Work Full type3 simulation ISE-TCAD input files prepared. Accounts and ISE-TCAD setup at HPC. Beowulf in-house cluster under construction. Estimate node points required. More complete architecture simulations. Matching simulations to experiment. Convert type3 simulation to replicate macroscopic charge-qubit experiment.

Type3 Device electron and hole (spin-qubit) A circuitry interlude: hole electron Nano-circuits are pretty darn small.

Integrated Systems Engineering – Technology Computer Aided Design I S E – T C A D Software package designed for microchip industry. Orthodox approach to single-electron tunneling. Extend ISE-TCAD to nanotech/mesoscopic devices. MESHDESSISPICASSO User specifies mesh spacing to vary over regions of interest. coarse fine Poisson’s Equation AC analysis Graphical user interface for visual analysis of simulations.