Interface magnons with superconducting quantum circuits

Transcription

1 Interface magnons with superconducting quantum circuits Magnon-polaritons from room temperature down to millikelvin temperature Martin P. Weides Johannes Gutenberg University Mainz, Germany and Karlsruhe Institute of Technology (KIT), Germany

2 Introduction QuantumMagnonics Superconducting quantum circuits Multi-level spectroscopy, magnetic dipole qubit, high coherence Magnonics Classical to quantum 2

3 Magnonics: spin waves in nanostructures Magnon: quantized spin wave excitation Future information technology (e.g. spin-torque oscillator, spin-wave propagation control for logic) Slavin et al., Nat. Nanotech. 09 Vogt et al., Nat. Commun. 14 Linewidth Δf > 1 MHz Attenuation length ~10 um Strong magnon damping: magnon/phonon/electron scattering Grand challenge: To understand physics, single magnon information needed! 3

4 Status quo 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) scattered incident magnon Difficult to access magnon ground state! 4

5 How to probe a single magnon? 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 5

6 Coherent coupling requirement Strong coupling: Qubit Magnon < 1 MHz Ni 80 Fe 20 < 50 MHz, Y 3 Fe 5 O 12 < 5 MHz Coupling rate g (N number of spins in qubit mode volume V 0 ) > 10 MHz (strong coupling) 6

7 Introduction QuantumMagnonics Superconducting quantum circuits Multi-level spectroscopy, magnetic dipole qubit, high coherence Magnonics Classical to quantum 7

8 Transmons: capacitively shunted Josephson junction Anharmonic oscillator Non-linear, tunable LC oscillator Two lowest levels Bloch sphere Φ Magnetic flux Φ changes L J (φ) 8

9 KIT quantum lab Al, Nb, NbN films Al-AlO x -Al tunnel junctions (shadow evaporated) Lithography, etching (Nanostructure Service Laboratory) He 3 /He 4 dilution fridge (40cm base plate) 18 RF & 24 DC lines, filters, 5 amps 9 quantum chips 200 nm Spectroscopy, time-domain setups Software (simulation, measurement) QKIT on GitHub 9

10 Anharmonic many-level quantum circuit transmon qubit: weak anharmonicity Consider higher quantum levels efficient & robust quantum gates enhanced security of key distribution in quantum cryptography quantum simulation spin-½ two levels spin-1 three levels Neeley Nat. Phys. 4 (2008) Fedorov Nat. 481 (2011) Bruß PRL 88 (2002) Cerf PRL 88 (2002) Paraoanu JLTP 175 (2014) 11

11 Qubit sample TL microstrip geometry Sandberg APL 102 (2013) overlap Josephson junction transmon regime: ~0.05 spectroscopic measurements VNA readout tone microwave drive/probe tone Koch PRA 76 (2007) Blais PRA 69 (2004) 12

12 High power spectroscopy excitation tone (GHz) /2 1 2 /2 1 3 /2 1 4 /2 dispersive resonator shift Multi-photon transitions determine qubit parameter E J, E C Koch et al. PRA Braumüller et al., PRB 2015

13 Multiphoton dressing pumping the -level Sweep drive & probe freqs. measurement simulation Dynamical coupling of levels by probe tone Autler-Townes doublet like avoided crossing 14 Braumüller et al., PRB 2015

14 Transmon qubit Concentrically shaped electrodes 4 cos Operation in phase regime, Koch, PRA 76 (2007) pad geometry dipole antenna concentric geometry reduced radiation/crosstalk Sandberg, MW, APL 102 (2013) 15

15 Geometry of concentric, gradiometric transmon Central island and concentric ring electrode, interconnected by two Josephson junctions, ~120 Gradiometric dc-squid loop fast frequency control Dispersive qubit readout 16

16 Main features Hybrid coplanar/microstrip design Minimize defect loss at surface and interface oxides Straightforward fabrication: Optical lift-off lithography Electron beam lithography, shadow-angle evaporation 17

17 Pulsed (time-domain) measurement setup 18

18 Dissipative dynamics Loss contributions Purcell Γ 16μs Dielectric defects Γ 26μs Γ 9μs Radiation Γ 100μs 19

19 Qubit coherence Hahn echo sequence 20

20 Pulsed measurements fast control of qubit frequency 21 Braumüller et al., APL (2016)

21 Fast qubit tuning Full tomographic control z y Measured Expected x SSB-mixing, shaped pulses (DRAG) Gate benchmarking (99.54%) 22

22 Consider geometric loop inductance Artificial spin array with non-trivial couplings (analog) spin system simulation Good agreement for 0.6nH Reiner, Marthaler, Braumüller, MW, et al. arxiv (2016) 23

23 Quantum SWAP (Qubit-Resonator) 1. Excite qubit off-resonance to resonator 2. Bring on-resonance and hold for t 3. Detune qubit and readout P 0 P 1 Quantum-Setup works! DC & RF electronics, pulse shaping, bias tee, software Controlled quantum SWAPs (qubit-ho) 24

24 Introduction QuantumMagnonics Superconducting quantum circuits Multi-level spectroscopy, magnetic dipole qubit, high coherence Magnonics Classical to quantum 25

25 Yttrium iron garnet (Y 3 Fe 5 O 12 ) Electrically insulating ferrimagnet Empty 4s, half filled 3d orbitals no orbital momentum, s=5/2 Five Fe 3+ ions per unit cell form sublattices of opposing magnetization approximated as ferromagnet Extremely low spin-wave damping spin wave decay length on the order of centimeters T Curie = 559K High spin density ρ= /m 3 Anisotropic, [110]-axis is soft magnetic 26

26 Magnons Quasiparticles, collective excitation of the electrons' spin structure in crystal lattice Outer magnetic field H removes degeneracy Precessional motion of magnetization M, Landau Lifshitz eq. k=0 precessing macrospin with Kittel resonance frequency 27

27 Spin waves affect static and dynamic magnetization Spin wave: spin-lattice excitation in magnetically ordered material Harmonic variation (wavelength ) in phase of precession of adjacent spins about the local magnetization direction (parallel to magnetic field ) Single magnon= flip (i.e. 180 rotation) of a single spin Saturation magnetization S Change in static magnetization: Δ Z = S (1 cos ) notional precessional angle of spins about magnetization direction AC magnetization perturbation (vector rotating at magnon frequency ) Δ AC = S sin in-plane perpendicular to Δ Z. For small : Reduction in static magnetization Δ Z S 2 /2 Increase in dynamic magnetization Δ AC = S 28

28 Magnon-Cavity experiments (incomplete ) Since 2014 rapid growth of publications Tabuchi et al. PRL 2014 Hybridizing Ferromagnetic Magnons and Microwave Photons in the Quantum Limit Zhang et al. PRL 2014 Strongly Coupled Magnons and Cavity Microwave Photons Goryachev et al. PR Applied 2014 High-Cooperativity Cavity QED with Magnons at Microwave Frequencies Cao et al. PRB 2015 Exchange magnon-polaritons in microwave cavities Zhang et al. NPJ 2015 Cavity quantum electrodynamics with ferromagnetic magnons in a small yttrium-iron-garnet sphere Tabuchi et al. Science 2015 Coherent coupling between a ferromagnetic magnon and a superconducting qubit Bourhill et al. arxiv 2016 Ultra-High Cooperativity Interactions between Magnons and Resonant Photons in a YIG sphere 29

29 3d cavity resonator Magnetic field distribution YIG sphere 30 1 st mode 2 nd mode Marcel Langer BA thesis KIT (2015)

30 3d cavity-kittel mode (YIG) strong coupling Two setups (classical and quantum) 4 to 300 K Up to Tesla-fields Extend to thin films Few/ single magnon excitations (mk) Linewidth and noise Extend to qubit 31

31 Temperature dependence down to 5K Reentrant cavity, see Goryachev et al. PR Applied 2014 Reducing temperature Coupling strength g increases Resonant magnetic field decreases Additional modes appear & disappear cf. Zhang et al. NPJ

32 Approaching quantum: magnon-polaritons at 500mK Extraction from fit κ in = 65 khz κ m = 2.4 MHz Non-uniform modes visible κ r = 0.9 MHz g= 27.8 MHz 33

33 Coupling qubit to magnon + qubit readout resonator (not shown) Straightforward: coupling via 3d cavity (modes for coupling, Q-readout) Tabuchi et al., Science

34 Transmon qubit coupled to 3d cavity 3d cavity: quantized field suppresses radiative loss low E-fields and weak coupling to surface TLSs Long coherence T 1 15 µs, T 2 16 µs, T 2* 30 µs 35 Grünhaupt MA thesis (2016)

35 Hybrid quantum systems Dry 10mK fridge (July `16) Magnon-polaritons from RT 0.5K YIG sphere and thin films Spectroscopy and pulsed measurement setup ready 36

36 QKIT framework - an extension to qtlab written in python Open-source measurement software QKIT Collection of ipython notebooks for measurement and data analysis hdf5 based data storage of 1,2 and 3d data 1 and 2d data viewer Extended and maintained drivers for low and high frequency electronics Large parts of the framework can be used independently of qtlab Classes for data fitting, e.g. of microwave resonator data. This includes also a robust circle fit algorithm (Probst et al. Rev. Sci. Instrum. 86, (2015)) 37

37 Team BA MA PhD Technician Oliver Hahn Julius Krause Jochen Braumüller Lucas Radtke Moritz Kappeler Lukas Grünhaupt Marco Pfirrmann Tomislav Piskor Yannick Schön Steffen Schlör Scientists Patrick Winkel Andre Schneider Hannes Rotzinger Max Zanner Ping Yang Sasha Lukashenko Alexey Mainz Isabelle Boventer Mathias Kläui 38

38 Thank you for your attention 39