8/9/2019 Cavity QED for donor spin qubit in silicon

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Cavity quantum electrodynamics foroptical manipulation of spin qubits in silicon

Salahuddin Nur Supervisor: Dr. John J. L. Morton

Electronic Materials and Devices Research Group, Department of Electronic & Electrical Engineering, UCL

V. Cavity quantum electrodynamics for QIPCavity quantum electrodynamics:

study of interaction between light and particles in a cavity. treats the modication of the emission properties of emitters

both strong and weak coupling regime are useful in QIP

Purcell Effect:

emission depends on the electromagnetic environment tailored cavity can enhance spontaneous emission observed in weakly coupled cavity

V. Optical manipulation of donor spin in siliconOptical control over spin qubit promises:

very fast gate operation low-power ying qubit single donor control

quantum network

,e ,

0 1

Optical readout of doner spin in silicon is difficult:

indirect electronic bandgap

dominant Auger recombination reabsorption of emission free carrier absorption

E n e r g y

X

L

Wave vector

Electrons

Holes

h v

InP Si

Directrecombination

Free-carrierabsorption

Augerrecombination

PhononIndirectrecombination

neutral donor

neutral donorbound exciton

Radiativeexcitation and recombination

+

+

_

_

+

_

I. Abstracte realization of efficient optical spin manipulation technique in silicon would

provide a near-ideal quantum information processing (QIP) system. However,optical spin manipulation in silicon is challenging due to the presence of an indi-rect bandgap. In this work, we research the potential of implementing a photoniccrystal nanocavity for enhancing spontaneous emission and photon extractionefficiency to develop optical control techniques for donor spins in silicon.

II. Silicon as a platform for QIPAdvantages of Silicon based QIP systems:

Matured fabrication technology Scalable realization Low spin-orbit coupling Near zero nuclear spin environment

Long coherence time

Electron Nucleus

T1 T 2 T 1 T 2

1 s

1 ms

1,000s1 h

1 min

Si:P (ESR)

Si:P (EDMR)

Si:BiSiGe quantum dotMOS quantum dot

|0

|1

T2

T1

28 Si:Sb (Near surface)

28 Si:P (ESR)

Donors in silicon:

are impurities with an extra electron resemble hydrogen atom at low temperatures promising candidate for qubit realisation

31 P

e n2

e1 e2

n1

Donor bound excitons and their recombination in silicon:

HHLHSO

E

-X X

k 0k 0

k

D 0 X recombination E

-X X

k 0k 0

k

Donor-bound exciton (D 0 X)

E NP Radiative

recombination

Augerrecombination

an exciton is an electron and a hole bound by Coulomb force bound excitons are excitons localized at impurity atoms

Nuclear spin

Electron spin

VI. Photonic crystal cavity for enhanced emissionPhotonic Crystals:

periodic arrangements of dielectric media photonic semiconductors allow unprecedented control over light provide electromagnetic cavity if doped can tailor spontaneous emission 0

0.1

0.2

0.3

0.4

0.50.6

0.7

0.8

TM modes

TE modes

M K

Photonic Band Gap

M K F r e q u

e n c y

a / 2

c

r

a

z

x y

Enhancement of light emission by photonic crystal cavities:

the total efficiency of light emission from an emitter can be expressed (total) = (emission) (extraction) (collection) photonic crystal can enhance all three of them with careful design

Light emission from crystalline silicon photonic crystal cavities:

Critical issues for getting purcell enhancement:

weak coupling, spectral and spatial matching of emitter narrower emitter linewidth, high quality factor and low mode volumeDonor bound excitons in silicon photonic crystal cavity:

has significant potential for optical manipulation of donor spin and QIP has not been investigated thoroughly yet! the main focus of this work!

I. Quantum information processing Quantum Computer:

utilises quantum mechanics to carry out computation uses quantum state superposition and entanglement. can test a vast number of possibilities simultaneously

Qubit: unit of quantum information, quantum analogue of the classical bit coded in two-level quantum systems

'

Classical Bit vs. Qubit (Quantum bit)

1

0

(Classical Bit)

Bit Number

|1>

|0>

Bit Number

(Quantum Bit)

VII. ConclusionEnhancement of no phonon emission from donor bound excitons in silicon pho-tonic crystal cavity has signicant potential due to the features such as narrowemitter linewidth, low temperature operation, high quality factor and low mode volume of the cavity. Enhanced no phonon transition can make optical control ofdonor spin qubit a reality. is potential makes the research very attractive eventhough there are several challenges to overcome.

References:1. J. J. L. Morton, and et al., Nature 479, 345 (2011).

2. J. J. Pla, and et al., Nature 496, 334 (2013). 3. Y. Yamamoto, et al., Physica Scripta 2009, 014010 (2009). 4. J. Joannopoulos, and et al., Photonic Crystals: Molding the Flow of Light, 2008

5. S. Iwamoto and et al., IEICE Transactions on Electronics E95.C, 206 (2012). 6. M. Fujita, and et al., IEEE Journal of Quantum Electronics 14, 1090 (2008). 7. N. Hauke, and et al., New Journal of Physics 12, 053005 (2010).

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