low noise single electron source

Low NoiseSingle Electron Source

Jin Zhang , Yury Sherkunov, Nicholas d’Ambrumenil, Boris Muzykantskii

University of Warwick, U.K.

Conference on Computational Physics 2009, Kaohsiung, 16th, Dec.

)(tV

Single Electron Excitation

Arbitrary Pulse:

t

dttVt ')'()()(tie

FkFk

Single Electron Excitation

2 2

2( )V tt

Minimal Excitation States (MES):

( )i t t iet i

Ivanov Lee Levitov, Phys. Rev. B 56, 6839

Keeling Klich Levitov, Phys. Rev. Lett. 97, 116403

t

dttVt ')'()(

FkFk

Noise Characterization

D)D(12 pt

QPartition Noise:

Thermal Noise:

eqQ

thQ

ptQQ 2222

f2 DTtth

Q

Equilibrium Noise (T=0):

DD

)εDlog(t Ff2 eq

Q

fFtvL

0 t

D

ft

Noise Minimization

Minimized by setting

0

D

t

for abrupt opening at GHz

?0t

D

ft

D

Low temperature -- mKHigh frequency -- GHz

),1(2 DDpt

Q 1D

),εDlog(t Ff2 eq

Q

,DTt f2 th

Q

1

Suppression of the Equilibrium Noise1. Single Lorentzian pulse to the barrier

2. Double Lorentzian pulses to the barrier

11

11

11

11

22

22Im)(

ittitt

ittitttA

( ) Im t iA tt i

When 0.8 (0) 1A

2|)(|)( tAtD

212

eqQ

412

eqQ

1

1

1

21

21

t

Low Noise Single Electron SourceTotal noise from single electron emission:

JZ YS NdA BMPhys. Rev. B 80, 245308

Phys. Rev. B 80, 041313 (R)

Probability Distribution:

High yield singleelectron emission

Suppressed multipleelectron emission

20

20

0

)(2)(

tttV

10

Conclusion

• Suppressing the quantum equilibrium noise at low temperature by tuning the tunneling barrier (QPC) transparency

• Low noise on-demand single electron source at low temperature

Many thanks for your attention!

Single Electron SourceFève et.al, Science 316,1169

Averaged over millions of eventsToo Noisy

Working Condition: GHz, mK

Keeling et.al, PRL 101, 196404

Minimize the Noise?

Optimal Electronic EntanglerApply Single Lorentzian pulse to the barrier

( ) Im t iA tt i

212 Q

“useful”, 1Q 0QNot “useful”

No excessive not “useful” noise at all

50% Entanglement efficiency,Theoretical maximum

Theory ofFull Counting Statistics (I)

( ) i nn

n

P e

Characteristic Function

Current, Noise, etc...0

ln( )

mm

mQi

Understood with density matrix of outgoing states:

)'()',()()'()',()( tBttntBtAttntAbbn inR

inLRR

outR

R

Lti

ti

R

L

aa

S

tBetAetAtB

bb

)()()()(

)(

)(

Theory ofFull Counting Statistics (II)

Abanov et.al 20082 (1 )j j

j

Q n n

jn

jn

ji

jj nQenn ,)1()( 1,)1()( j

ijj nQenn

jj

iniQi neee j )1(1)(

Non Optimal PulsesFor finite cut-off, additional noises are induced