Ultrafast Pulsed Laser Gates for Atomic Qubits

JOINTQUANTUMINSTITUTE

with David Hayes, David Hucul, Le Luo, Andrew Manning,Dzmitry Matsukevich, Peter Maunz, Jonathan Mizrahi,

Steven Olmschenk, Qudsia Quraishi, Crystal Senko, Jon Sterkand Chris Monroe

Wes CampbellU. Maryland and NIST Joint Quantum Institute (USA)

ECTI Durham, UKSeptember 23, 2010

Things that are scary:

Ghosts!

Mode-locked lasers: less scary (?)

PSD

•ps – fs pulse durations•repeatable and clean

]

sech[)(pulseT

ttE

FSR = frep

FSR

Mode-Locked Laser Gates

•Raman transitions: Strong excitation regime

fast single qubit operations

an approach for fast entanglement

•Raman transitions: Weak excitation regime

your favorite cw tasks done with a comb

entanglement of two ions

•Resonant transitions: excite to the P state

photon frequency or polarization qubit

remote entanglement of two ions

171Yb+ spin ½ nucleus

2S1/2

2P1/2

12.6 GHz

hyperfine clock state qubit

370 nm

S. Olmschenk et al., PRA 76, 052314 (2007)

171Yb+ spin ½ nucleus

2S1/2

2P1/2

12.6 GHz

state preparation:optical pumpingS. Olmschenk et al., PRA 76, 052314 (2007)

State detection with 171Yb+

2S1/2

2P1/2

12.6 GHz Number of de tected pho tons

Num

ber

of

exp

erim

ents

in th

ousa

nds

0

2

4

6

8

10

12

14

16

0 5 10 15 20

simple discriminatordetection fidelity 98.5%

Number of de tected pho tons

Num

ber

of

exp

erim

ents

in th

ousa

nds

0

2

4

6

8

10

12

14

16

0 5 10 15 20Number of de tected pho tons

Num

ber

of

exp

erim

ents

in th

ousa

nds

0

2

4

6

8

10

12

14

16

0 5 10 15 20

S. Olmschenk et al., PRA 76, 052314 (2007)

• Ions for QI preparation, storage, and readout• Photons for QI transmission, communication

ion-photon entanglement

•Bandwidth must exceed qubit splitting(s)•Excitation probability I

~~

pico-second pulses

Pulse width considerations

10 ps 70 GHz

Ion-photon entanglement

2S1/2

2P1/2

12.6 GHz

L.-M. Duan et al., PRA 73, 062324 (2006)

Prepare ion in an arbitrarystate

01 o

excite ion to P state with aπ-polarized picosecond pulse

collect π-polarized photon

01 f R B

• Long Distance• atomic motion insensitivity• No optical interferometric

stability necessary• Hybrid systems• Probabilistic but scalable

Simon and Irvine, PRL, 91, 110405 (2003)

non-local QIP viaphoton coincidence detection

Ion-Ion entanglement

P. Maunz et al., PRL 102, 250502 (2009)

click! click! coincidence detection meansphotons were in state

which heralds the ion-ion state

2121

photons R RB B

21

)2()1()1( )ˆˆ(ˆ ionionzzz I

Photon-mediated entanglement of distant (~1 m) atomic qubits

P. Maunz et al., PRL 102, 250502 (2009)

• Private random numbers

• Bell inequality test

• Quantum teleportation

• Remote entangling gate

S. Olmschenk et al., Science 323, 486 (2010)

S. Pironio et al., Nature 464, 1021 (2010)

D. N. Matsukevich et al., PRL 100, 150404 (2008)

want better photoncollection efficiency

enhanced light collection

12

g

C 2.01.0124

C

Cd

“Decent” cavities G. Guthorlein, et al., Nature 414, 49 (2001)A. Mundt, et al., Phys. Rev. Lett. 89, 103001 (2002)W. Keller,et al., Nature 431, 1075 (2004)

• Time-bin photonic qubit

Insensitive to birefringence,

dispersion

Cavity length free parameter

Time-bin resolving detectors

give other entangled states

p

Light collection: Innsbruck, NIST, Aarhus, Sussex, Saarbrucken, Sandia,

Singapore, Duke, GTRI, Erlangen, MIT, Griffith, Washington, JQI,…

early

photonlate

photon

earlylate

Fastp

Fast

Stimulated Raman transitions

Single photon detuning D

•Spontaneous emission

Optical power = speedand low laser-induceddecoherence

2

I

•Diff. ac Stark shifts 2

I

•Raman Rabi Freq.

I

Raman

Raman Laser Wavelength

2S1/2

2P1/2

12.6 GHz

2P3/2329 nm

370 nm

Δ = 33 THz

Δ

5×10-5

4×10-5

3×10-5

2×10-5

1×10-5

0

Spontaneous emission

340 350 360 370 3800

1 105

2 105

3 105

4 105

.00005

0

P x( )

W x( )

380340 x

spont

340 350 360 370 380

5, 10sponP

Wavelength [nm]

Pulsed laser Raman transitions

Short pulse = large bandwidth•10 ps pulse gives 70 GHz

Short pulse = easy UV•Single-pass SHG, THG, etc.

No need for HF / UV EOM

No need for buildup cavity

Pulsed Raman Transitions:Strong Excitation Regime

Fast.

, temperature,Not very sensitive to

“bang-bang” dynamic decoupling, super-fastcooling (see Machnes hot topic talk), photontime bin qubit, rep rate limited experiments

Speed for improved coherence

Slow QIP Fast QIP

We want fast gates for both speed and fidelity

Strong Pulse Raman Transitions:Rosen-Zener Solution

Nathan Rosen and Clarence Zener (PR 40, 502 (1932)):

xz

tH

ˆ2

)(ˆ

2HF

2sech

2sin pulseHF2pulseo2

ex

TTP

pulseo

sech )(

T

tt

Rabi flopping contrast

Strong Pulse Raman Transitions:pulse duration limited transfer

~70%Single Pulse Rabi Flop

ps 15pulse T

2sech

2sin pulseHF2pulseo2

ex

TTP

Strong Pulse Raman Transitions:“pulse shaping”

pulse shape limits transfer

delayT

time

time

2

2

Strong Pulse Raman Transitions:Ramsey Spectroscopy

delayT time

s+ s-

40 psp-pulses

Strong Pulse Raman Transitions:Ramsey Spectroscopy

delayT time

Lin Lin

Momentumtransfer

Pulsed Raman Transitions:Weak Excitation Regime

X

Requirement:

Rep rate provides spectral sensitivity.

Zqf

f

rep.

qubit

Pulsed Raman Transitions:Weak Pulse Regime

Coherent accumulation of transition amplitude

313q

5.469q

Pulse Train Duration [ms]

Resonance Study for Rabi Flops qf

f

rep.

qubit

5.469q

313q

D. Hayes et al., PRL 104 140501 (2010)

Weak pulse Raman transitions:accessing motion

trapqubit ff

mode-lockedlaser

AOM

trapf

qubitf

rep.f

AOMf

qubitf

Weak pulse Raman transitions:accessing motion

mode-lockedlaser

AOM

trapqubit ff trapqubit ff trapqubit ff trapqubit ff trapqubit ff trapqubit ff trapqubit ff trapqubit ff trapqubit ff trapqubit ff trapqubit ff

standard trapped ion QIP tasksdone with an optical frequency comb

Single qubit operations Sideband cooling

Spin-motion entanglement

AOM Frequency (MHz)200

0,1 1,0 1,1

0,0

1,1 0,1 1,0

201 202 203

N t rep 1

P( )

0.1

0.6

P( )

0.7

0.07.1

Detuning from carrier transition (MHz)

65.1 6.1 6.1 65.1 7.1

Blue SidebandRed Sideband

0.02 0.01 0.00 0.01 0.020.0

0.1

0.2

0.3

0.4

0.5

MHz

P

D. Hayes et al., PRL 104 140501 (2010)

C

1

1

0

2

0

Mølmer-Sørensen gate

Low-decoherence Raman transitions

2S1/2

2P1/2

12.6 GHz

2P3/2

329 nm

370 nm

• Low AC Stark shift (10-4Ω)• Low spon. emiss. (10-5)

• High UV power (4-10 W)

(Emily Edwards hot topics talk Friday)

Mode-Locked Laser Gates

•Raman transitions: Strong excitation regime

fast single qubit operations

working toward fast entanglement

•Raman transitions: Weak excitation regime

your favorite cw tasks done with a comb

low decoherence

•Resonant transitions: excite to the P state

entanglement of distant ions via photons

need increased light collection

Postdocs Kihwan KimLe LuoQudsia QuraishiEmily EdwardsSusan Clark

Grad StudentsDavid HayesDavid HuculRajibul IslamSimcha KorenblitAndrew ManningJonathan MizrahiCrystal SenkoJon SterkShantanu Debnath

UndergradsBrian FieldsKenny LeeAaron Lee

JOINTQUANTUMINSTITUTE

Alumni PeterMaunzStevenOlmschenkDzmitryMatsukevich

P.I.Chris Monroe

Duke

NIST

Singapore