PBG CAVITY IN NV-DIAMONDFOR QUANTUM COMPUTING

Team:John-Kwong Lee (Grad Student)Dr. Renu Tripathi (Post-Doc)Dr. Gaur Pati (Post-Doc)

Supported By:DARPA, AFOSR

OPERATIONS NEEDED FOR A QUANTUM COMPUTER

STATE PREPARATION: e.g. OPTICAL PUMPING

SINGLE BIT OPERATION: e.g. -PULSE

TWO-BIT OPERATIONS: e.g. CNOT

METHOD: LASER CONTROLLED SPIN EXCITATION (DARK RESONANCE)

MEDIUM: SHB CRYSTAL, e.g. NV-DIAMOND

o o o o o o

21 M M+1 N

frequency

LASER 1

LASER 2

SINGLECAVITYPHOTON

SINGLECAVITYPHOTON

1

2

3

4

N

(1 cm)3

(5 m)3

KEY FEATURES:

SPIN AS QUBIT

>5000 OPS BEFORE DECOHERENCE

OPTICAL OPERATION & READOUT

OPTICAL INTERCONNECT POSSIBLE

NATURALLY SUITED TO TYPE 2 QC

SOLID STATE

SCALABLE TO >1000

PARALLEL POSSIBLE

BOTTOM LINES:

QUANTUM COMPUTING IN NV-DIAMOND: BASIC IDEA

|a> - |e> |b> - |e>

|a> + |e> |b> + |e>

|->=|b> |->=|a>

|+> - |e>

|+> + |e>

1

0AM

PL

ITU

DE

TIME

|-> = (2|a> - 1|b>)/|+> = (1|a> + 2|b>)/|e

|a|b

|e

|- |+

ADIABATIC TRANSFER VIA THE DARK STATE

TOPOLGICALLY ROBUST

EQUIVALENT TO A -PULSE

ATOM A

ATOM B

1 2

g

A B

0

g2

g1

A B

0

STEP 1: COHERENCE TRANSFER VIA CAVITY QED

METHOD 1: CAVITY ENHANCED COUPLING

AFTER ADIABATIC TRANSFER:ATOM A -- PURE STATEATOM B -- PRODUCT STATE“CNOT” WITH RAMAN PULSE

e n

ATOM B

2

0

2

0

g

2

2

2

g

2

ATOM A

01

1

0

g

1

1

1

g

1

COHERENCE TRANSFER VIA RAMANINITIAL CONDITIONS:ATOM A -- ELECTRON COHERENCEATOM B -- NUCLEAR COHERENCE

ATOM A

0

0

PURESTATE

1 2

1 2

1 2

1 2

ATOM B

PRODUCTSTATE

RAMAN C-“NOT” e n

STEP 2: ENTANGLEMENT (CNOT) VIA CAVITY QED

2

1

0

1

INT

EN

SIT

Y

TIME

ADIABATIC COHERENCE TRANSFER

ATOM 1

ATOM 2

1 2

g

CAVITY VACUUM COUPLING g

ATOM 1 ATOM 2

|a1> |b1>

|e1>

1 g

|a2> |b2>

|e2>

2 g

INITIAL

RAMAN DARK STATES

|a1 b2 0> |b1 a2 0>

1 g 2g

|b1 b2 1>

|e1 b2 0> |b1 e2 0>

2 g 1 g12

|b1 b2 0>

NO CAVITY PHOTONS

ONE CAVITY PHOTON

ADIABATIC COHERENCE TRANSFER VIA CAVITY-QED DARK STATE

DARK STATE QUANTUM COMPUTING IN NV-DIAMOND: NECESSARY ENERGY LEVELS

a

c

QUBIT 1 QUBIT 2

b

d a

c

b

d

e f

e f

g h g h

DARK STATE QUANTUM COMPUTING IN NV-DIAMOND: ROLE OF STORAGE LEVELS

a

c

b

d

e fa

c

b

d

e f

a

c

b

d

e fa

c

b

d

e f

EXPLICIT CONSTRUCT FOR ENTANGLEMENT

a

c c a

c

c

c

b

aa

a

c b

DARK STATE QUANTUM COMPUTING IN SHB CRYSTAL: CANDIDATE MATERIALS

g h

a

c

b

d

e f

4.6 MHz4.8MHz

10.2 MHz

17.3 MHz

2mI

531

f

1

3

5

3H4

1D2

g h

a

c

b

d

e f

P

Q

4.6 MHz

2.8 MHz

f

3A1

3E

IZ

1-10

1

-1

0

SZ1 -1Sgn(mI)+ -

[A] [B]

IZ

-110

-1

1

0

Pr:YSO NV-DIAMOND

ISSUES WITH N-V DIAMOND

SPIN-ORBIT COUPLING SOMEWHAT INHIBITED

• RAMAN TRANSITIONS PARTIALLY FORBIDDEN

• WORK NEAR ANTI-CROSSING, LEVELS MIX

PERMANENT HOLE BURNING

• NO CW SIGNAL, CITE RE-ARRANGEMENT

• RE-PUMP ON PHONON SIDEBAND

2.88GHz

S= ±1

S= 0

B-FIELD0 1050 G

120 MHz

638 nm

ZEROPHONONLINEPHONON

SIDEBAND

AB

SOR

PT

ION

WAVELENGTH (nm)638514

ARGONLASERREPUMP

DYELASER

18

SPOT SIZES: ~ 0.3 mm

INTENSITIES:COUPLING -- 14 mW 13 W/cm2

PROBE -- 14 mWREAD -- 16 mW

C

R

P A

D

SPOTS ON SCREEN

BRAGGMATCHED

ARGONREPUMP

ARGONDYE

AOM

AOM

AOM

SCREEN

APD

D

A

C

P

R

DIAMOND

B-FIELD

APERTURE

LO

EXPERIMENTAL SETUP FOR DARK RESONANCE IN DIAMOND

SIGNAL(BEAT W/ LO)

S = 0

S = -1

120 MHz

20 MHz

P CD R

~638nm

120 MHz

S = 0

20 MHz

RD

P C

S = -1

-20 -10 0 10 20

0.00

0.06

0.12

0.18

0.24

0.30

0.36

0.42

0.48

0.55

5.5 MHz

Detuning Frequency (MHz)D

iffra

ctio

n E

ffici

ency

(%

)

DETECTION OF OPTICALLY INDUCED SPIN ALIGNMENT IN NV-DIAMOND

CAN BE INTERPRETED AS SPATIALLY VARYING COLLECTIVE SINGLE SPIN OPERATIONS

120 MHz

LEVEL DIAGRAM

S = 0

S = -1

P C

EIT AS EVIDENCE OF EFFICIENT STATE PREPARATION IN NV-DIAMOND

-20 -10 0 10 200

8

16

24

32

40

48

56

64

8.5 MHz

Probe Beam Detuning (MHz)

EIT

am

plitu

de (

%)

PP

C

NDFWM SIGNALS:•CENTRAL FREQUENCY 120 MHZ•COUPLING 7 W/cm2 = 1.4 Isat

•PROBE 1 W/cm2 = 0.3 Isat(SCANNED)•READ 4 mW•SPOT SIZE 300 m

120 MHz

LEVEL DIAGRAM

S = 0

S = -1

20 MHz

P CD R

~638nm120 100140DIFF. FREQ. (MHz)

INT

EN

SIT

Y (

AR

B.)

ANTI-CROSSINGB = 1050 G

AOM TUNING LIMIT

SPIN ALIGNMENT AMPLITUDE VS. MAGNETIC FIELD STRENGTH

10CONTROLLED NOT WITH NEAR DIPOLE-DIPOLE INTERACTION

APPLY OPTICAL 2 PULSE WITH 1• CONTROL ATOM IN |b 2>, NOTHING HAPPENS --EXCITED STATE SPLIT, 1 NOT RESONANT• CONTROL ATOM IN |c 2>, SIGN |c1> IS REVERSED: | c1 c2> - | c1 c2>• PHASE SHIFT GATE• EQUIVALENT TO CONTROLLED-NOT IN ROTATED BASIS

Frequency of 1

Abs

orpt

ion

of

1Excites optical

transition

Noexcitation

g = 0.006 (/r)3 (A B)

ATOM 1TARGET

ATOM 2CONTROL

|c1>|b1>

|a1>

|b2>|c2>

|a2>

g g

1

|c1>

|a1>

1

|c1>

|a1b2>- |b1a2>

|a1b2>+ |b1a2>

1

g

ATOM IN |b2> ATOM IN |c2>

CONTROL-NOT WITH DIPOLE-DIPOLE INTERACTION

METHOD 2: DIPOLE-DIPOLE INTERACTION

300 nm 20 nm

Diamond

SiO2

SiO2

Hole filled with nonlinear-opticglass

SiO2

SiO2

Holes filled withnonlinear-opticglass

Anomalous hole also filled withnonlinear-optic glass

Cavity

HIGH

LOW

HIGH

LOW

PMMA (E-Beam Litho)

SiO2 (CF4/CHF3 RIE)

Polyimide (O2 RIE)Alumina (BCl3 RIE)SiO2 (CF4/CHF3 RIE)

Diamond (O2 RIE)SiO2

SIMULATION OF THE TWO-DIMENSIONAL ISING MODEL, ISOMORPHIC TO THE PROBLEM OF THE MAXIMUM INDEPENDENT SET