Multiphoton dressing of an anharmonic superconducting many ... · Neeley Nat. Phys. 4 (2008) FedorovNat. 481 (2011) Bruß PRL 88 (2002) Cerf PRL 88 (2002) Paraoanu JLTP 175 (2014)

Multiphoton dressing of an anharmonic

superconducting many-level quantum circuit

Martin P. Weides

Johannes Gutenberg University Mainz, Germany

and Karlsruhe Institute of Technology (KIT), Germany

June 4th 2015

Quantum Metamaterials Workshop QMM Spetses

J. Braumüller, J. Cramer, S. Schlör, H. Rotzinger, L. Radtke, A. Lukashenko, P. Yang,

S. T. Skacel, S. Probst, M. Marthaler, L. Guo, A. V. Ustinov

Resonator

Qubit

fast-flux bias

300 µm

Martin Weides, QMM Spetses 2015 2

� Introduction

� Anharmonic many-level quantum circuit

� Power spectroscopy

� Dispersive resonator shift

� Rabi sideband transition of multi-photon coupled levels

� QMM � scale up! Concentric transmon qubits

� 2d qubits with 10us coherence

� Prospect

� QuantumMagnonics: qubits & spinwaves


Capacitively shunted Josephson Junction

� Anharmonic oscillator

Non-linear LC oscillator

Magnetic flux Φ changes LJ(φ)

Φ

Transmon qubit

Two lowest levels � Bloch sphere


Quantum lab

� Sputter tool (Al, Nb, NbN)

� Tunnel junction shadow evaporation (Al-AlOx-Al)

� Lithography and etching

� Large volume He3/He4 dilution refrigerator

�RF (18) and DC (24) wires, filters, amplifiers

�9 samples (6 qubits, 3 resonators)

� Time-domain setups (2), microwave spectroscopy

� Software (simulation, measurement)

200 nm

10 µm


� Introduction







� Prospect



Anharmonic many-level quantum circuit

consideration of higher quantum levels:

transmon qubit:

weak anharmonicity

Neeley Nat. Phys. 4 (2008)

Fedorov Nat. 481 (2011)Bruß PRL 88 (2002)

Cerf PRL 88 (2002)

Paraoanu JLTP 175 (2014)

enhanced security of key

distribution in quantum

cryptography

quantum

simulation

efficient & robust

quantum gates, qudit

JB et al., PRB 91 (2015)


Experiment

� microstrip geometry

� overlap Josephson junction

� transmon regime: �� ≫ �� ⇒ ��~0.05

� spectroscopic measurements

� VNA readout tone

� microwave drive/probe tone

TL

Blais PRA 69 (2004)

Koch PRA 76 (2007)

Sandberg APL 102 (2013)


Qubit spectroscopy40cm


Power spectroscopy – multiphoton transitions

� five bound states in Josephson potential

� dispersive shift scales with excitation

number ‹n›

Braumüller et al., PRB 2015


Dispersive shift of higher levels

� Rotating-wave Hamiltonian

� g01 = 115 MHz, ∆≈1 GHz


Qubit shift Resonator shift by qubit levels

|S21(ω

)|2


Power spectroscopy – simulation

measurement

simulation



Multiphoton dressing � − � , Rabi sidebands

� 0 , 2 degenerate in rotating

frame � dressing

� Probing of level structure (in

rotating frame) with weak

probe tone

measurement simulation


Sweep drive power Pdµω

& probe frequency ωpµω


Multiphoton dressing – pumping the |�⟩-level

Dynamical coupling of levels by probe tone

� Autler-Townes like avoided crossing

measurement

simulation


Sweep drive ωdµω

& probe ωpµω


Multiphoton dressing – pumping the |�⟩-level

measurement

simulation



� Introduction







� Prospect



Adding complexity12 qubits on-chip with local detuning

150 µm

Resonator

Flux bias I

Qubit

Transmission line

MA thesis J. Cramer (2015)

Φ

Coherence

T1=0.53 µs; T2 = 0.4 µs

5 mm


Novel design: Tunable concentric transmons

Devoret, Schoelkopf Science (2013)

� Long coherence: scalable quantum computation, error correction

� High experimental flexibility by fast flux tuning


Novel design: Tunable concentric transmon qubit (2d)

Coherence �� limited by energy relaxation ��

� Minimize surface/interface loss (TLS) � microstrip design

� Reduce radiative decay , i.e. qubit‘s dipole moment

� All Al-AlOx-Al technology

� Qubit: electron-beam

� All other: optical, lift-off

� Fast (ns) tunability

� Side-selective

inductive ��-coupling

Resonator

Qubit

fast-flux bias

300 µm


Concentric transmon qubit – low power spectroscopy

��/2�

1

2��/2�

excitation tone

dis

pe

rsiv

e r

eso

na

tor

shif

t


Concentric transmon qubit – high power spectroscopy

��/2�

1

2��/2�

exc

ita

tio

n t

on

e

dis

pe

rsiv

e r

eso

na

tor

shif

t

1

3��/2�

1

4��/2�


Concentric transmon qubit – flux spectroscopy

�� = 116MHz, �� = 69GHz, ��, = 138nA

�� ⁄ = 595

Φ

~ Idc


Pulsed (time-domain) measurements

Pulsed dispersive qubit readout

� resonator only driven during readout

to avoid state collapse (quantum

measurement)

Time-resolved qubit manipulation

� heterodyne single-sideband mixing

� quantum state tomography

to sample from sample


Pulsed measurements – Rabi oscillations

arg

�11

(a

.u.) |0〉

|1〉

� (��)


Pulsed measurements – Coherence

P1

P0

0 10 20 30

t [µs]

T1=9.1 µs

P1

P0

0 10 20 30

t [µs]

echo T2=10.2 µs


Pulsed measurements – fast z (energy splitting)-control


Pulsed measurements – Tomography, small detuning

decay from

1 2⁄ �|0〉 � |1〉� (x-axis)

� Long coherence qubits

�Measurement techniques (spectroscopic, pulsed)

�Quantum Simulation (Spin-Bose)

�Quantum Metamaterials (N Qubits- 1 Resonator)


� Introduction







� Prospect



Magnon: quantized spin wave excitation

Future information technology

(e.g. spin-torque oscillator, spin-wave propagation control for logic)

Strong magnon damping: magnon/phonon/electron scattering

Grand challenge:

To understand physics, single magnon information needed!

Slavin et al., Nat. Nanotech. ´09 Vogt et al., Nat. Commun. ´14

Attenuation length ~10 umLinewidth Δf > 1 MHz

Magnonics: spin waves in nanostructures


‘Classical measurement’:

� Inelastic scattering (neutron, photon, electron)

� Ferromagnetic resonance

Drawbacks:

� Weakly (not coherent) coupled

� Large flux, small signal (statistics)

� Thermally excited population (T > 4 K)

Difficult to access magnon ground state!

Status quo

magnonscattered

incident


� Quantum ground state (T=10 mK)

� Ultra-low power spectroscopy, coherent coupling

� How to achieve?

Extend magnon to artificial spin!

Access magnon lifetime and coherence via coherent coupling

How to probe a single magnon?


Strong coupling:

� Qubit < 1 MHz

� Magnon Ni80

Fe20

< 50 MHz, Y3Fe

5O12

< 5 MHz

Coupling rate g (N number of spins in qubit mode volume V0)

> 100 MHz (strong coupling)

Coherent coupling requirement


KIT-Team

BA

Cem Kücük

Marcel Langer

Tomislav Piskor

Alexander Stehli

Patricia Stehle

MA

Joel Cramer

Lukas Grünhaupt

Marco Pfirrmann

Steffen Schlör

Andre Schneider

PhD

Jochen Braumüller

Saskia Meißner

Sebastian Probst

Ping Yang

Technician

Lucas Radtke

Scientists

Michael Marthaler

Hannes Rotzinger

Sasha Lukashenko

Alexey Ustinov

NIST

Farnaz Farhoodi

Jeffrey Kline

Martin Sandberg

Michael Vissers

David Pappas


Thank you for your attention

Documents

Multiphoton dressing of an anharmonic superconducting many ... · Neeley Nat. Phys. 4 (2008) FedorovNat. 481 (2011) Bruß PRL 88 (2002) Cerf PRL 88 (2002) Paraoanu JLTP 175 (2014)