Sergey Frolov Vincent Mourik Ilse van Weperen Kun Zuo Erik Bakkers, Sebastien Plissard (TU/e &TUD)

Carlo Beenakker, Anton Akmerov, Fabian Hassler, Yuli Nazarov (Leiden & Delft)

Stevan Nadj-Perge Vlad Pribiag Johan van den Berg

NanoWire Team: spin-orbit qubits and Majorana Fermions

InSb Zinc Blende nanowires; length ~ 2-3 µm, diameter 80-120 nm

InSb

InAs stem

normal, Au contacts

Characterization by spin-orbit qubits experiments

Characterization using qubit techniques

few-electron quantum dots

spin-orbit level repulsion

electron spin resonance

source drain

gates

Quantitative numbers for Rashba spin orbit strength in InSb nanowires

Eso =2

2mλso2

λso = 200nm;Eso = 50µeV

α =2

mλso= 0.02eV ⋅nm

Eso

E BSO

k

n p n

Bia

s (m

V)

VPL(mV)

0

50

100

-50

-100

-500 -1000 -1500

gap 1h 2h 3h

d)

-1100 -1200 -1300 -1400

-700

-8

00

-900

VLG

(m

V)

VRG (mV)

-100

0

-1500

n p p n

a)

b)

(1,1)

(0,0)

(0,1)

(1,0) (2,0)

(0,2)

Freq

uenc

y (G

Hz)

2.5

7.5

12.5

B (mT)

-300 0 -300

I (pA

)

1.0

0

a)

b)

c)

Holes: interesting alternative for spin-qubits and Major.anas

B  

67⁰  

Contact  spacing                =  250  nm  

InSb  wire  Ti/NbTiN  contact  (10/100  nm)  Global  backgate  

Next: superconducting contacts

NbTiN technology from Klapwijk group

Rn = 1.4 kΩ

similar data from Marcus group on InAs wires and Xu group on InSb wires.

Supercurrents through InSb nanowires

NbTiN contacts, back gate only

Supercurrent!

I (n

A)

-2

2

I (n

A)

-2

2

I (n

A)

-1

1

Vgate (V) 20 60

B (T) 0 1 B (T) 0 0.4

nw B nw B

Induced superconducting gap: Δ* ≈ 700 µV @ B = 0 T      

4Δ*

co-tunneling spectroscopy

yellow line: EZ =±gµBB  

region between 0.3 and 0.5 T with: EZ > Δ*    

=> requirement for a topological superconductor

 

Majorana’s using nanowires; papers from 2010

•  Majorana Fermions and a Topological Phase Transition in Semiconductor-Superconductor Heterostructures Roman M. Lutchyn, Jay D. Sau, S. Das Sarma

•  Helical liquids and Majorana bound states in quantum wires

Yuval Oreg, Gil Refael, Felix von Oppen •  Tunneling characteristic of a chain of Majorana bound states

Karsten Flensberg •  Majorana fermions in multiband semiconducting nanowires

Roman M. Lutchyn, Tudor Stanescu, S. Das Sarma •  Quantized conductance at the Majorana phase transition in a disordered superconducting wire

A.R. Akhmerov, J.P. Dahlhaus, F. Hassler, M. Wimmer, C.W.J. Beenakker •  Anyonic interferometry without anyons: How a flux qubit can read out a topological qubit

F. Hassler, A. R. Akhmerov, C.-Y. Hou, C. W. J. Beenakker •  Non-Abelian statistics and topological quantum information processing in 1D wire networks

Jason Alicea, Yuval Oreg, Gil Refael, Felix von Oppen, Matthew P. A. Fisher •  Topological quantum buses: coherent quantum information transfer between topological and conventional qubits

Parsa Bonderson, Roman M. Lutchyn •  Interface Between Topological and Superconducting Qubits

Liang Jiang, Charles L. Kane, John Preskill

First set of experiments

van Dam, Nature 2006

•  tunneling – zero bias peak

•  topologically protected quantized conductance

•  4π periodicity in Majorana SQUID: I = Ic sin(φ/2)

Other zero-bias peaks

Van Wees et al., PRL 69, 510 (1992) Marmorkos, Beenakker and Jalabert, PRB 48, 2811(1993)

Reflectonless tunneling ⇒ peak at zero bias; around B = 0 up to one fluxquantum in area

Kondo effect ⇒ peak at zero bias; splits with Zeeman energy

“Nazarov peaks” ⇒ peak at zero bias; don’t stick to zero and move with B-field.

“Brouwer peaks” ⇒ Fermionic peaks at very low energy: move with B.

peaks come and go, but never stick to zero-bias

when changing B at B ≠ 0