modeling read-out for solid-state quantum computers in silicon
DESCRIPTION
Modeling Read-Out for Solid-State Quantum Computers in Silicon. Modeling Read-Out for Solid-State Quantum Computers in Silicon. Vincent Conrad Supervisors: C.Pakes & L. Hollenberg. Introduction. Solid-State Quantum Computers in Silicon. Single Electron Transistors. Modeling Read-Out. - PowerPoint PPT PresentationTRANSCRIPT
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
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 levelsPotential Barriers
TkE B
{
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 1st 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 theoryThe 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.
C
eCn
C
eCn
C
qnF oe 1221
2
2
)(
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
)()( ihhiee VVCVVCq
Charge Qubit Read-Out
Q = CV
)()( ''ihhihh VVCVVCq
Results
N.B. For charge qubit q is difference between two points.
= 2.49x10-2 e q = 2.14x10-2 e q
Conclusions
26min /102.3 qet
Induced island charge >> SET Sensitivity
Need an answer before information lossElectron-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 10-2 e >> 3.2 x 10-6 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 100 000 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:
holeelectron
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.
MESH DESSIS PICASSOUser specifies mesh spacing to vary over regions of interest.
coarse
fine
)()( 2
0
rVr
VCjVAI
Poisson’s Equation
AC analysisGraphical user interface for visual analysis of simulations.