Superconducting quantum circuit research -building blocks for quantum matter- status update from the Karlsruhe lab

Transcription

1 Superconducting quantum circuit research -building blocks for quantum matter- status update from the Karlsruhe lab Martin Weides, Karlsruhe Institute of Technology July 2 nd, mm

2 Basic potentials Harmonic oscillator Photons in cavity, atom oscillation Energy levels equidistant Anharmonic oscillator Large excitation amplitudes Energy eigenstate Two level system if /w >>0 two level system atomic transition, spin, qubit

3 Nobel price 2012 Nobel Prize in Physics 2012 was awarded jointly to Serge Haroche and David J. Wineland "for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems" Controlling a quantum particle (atoms or ions) Jaynes Cummings Cavity-qubit system

4 Quantum information processing, Q-simulation, Q-metamaterial Artificial atoms for quantum matter require Large interaction strength Tunability Frequency selection Long coherence High integration density dipole moment tune transition frequency large anharmonicity low loss scalability Smaller Bigger Atomic Mesoscopic Microscopic - Ions - Semiconductor Spins - Superconducting circuits - Neutral Atoms - NMR - Photons - Quantum Dots - Spin perfect DC conductor w/ low AC loss 100 mm

5 Microstructured quantum processor (University of California, Santa Barbara) Qubit Memory Signalbus Lucero et al., Nature mm

6 SUPERCONDUCTING RESONATORS AND QUBITS

7 Harmonic oscillator w/ superconductors C L LC (linear) oscillator No atom/qubit Coplanar waveguide resonator (l length) coupler w quality factor Q loss tangent d

8 Josephson junction non-linear inductor Phase difference 1 st Josephson eq.: (DC) 2 nd Josephson eq.: (AC) From DC: Insert in AC: non-linear inductance:

9 Capacitively shunted Josephson junction Anharmonic oscillator C L J, f non-linear LC oscillator C L J F v v L J Magnetic flux F changes L J (f) C 2 w w 10 Restrict to two lowest states Bloch sphere

10 Superconducting qubit zoo Charge 1 Flux 10 2 Phase 10 4 Junction area (μm 2 ) Modern designs C-shunted flux qubit Transmon= C-shunted charge qubit 100 mm 3d transmon

11 circuit quantum electrodynamics (cqed): artificial atom (qubit) coupled to resonator Strong coupling regime possible Resonator Qubit Koch et al. PRA 2007, Blais et al. PRA 2004 Transmission S 21 Qubit readout Frequency f r

12 Research goals Quantum material science Junctions, resonators Dynamical control of TLS, monitored with qubit Quantum simulation Spin-Boson system Multi-partite entangled systems

13 Parasitic two level systems (TLS) in dielectrics S I S E Josephson tunnel junction I S resonator Amorphous oxides loaded with uncompensated charges ~ /cm 3 Range of energies, coherence and Rabi frequencies, T 1, T 2, W Absorption probability goes as ~ Maximized at low E, T Dominating loss at low T & E Schickfus, Hunklinger (1975) Katz et al., PRL (2010)

14 Decoherence due to TLS w 10 S flux bias Qubit spectroscopy and time domain TLS located in tunnel barrier oxide E interaction S lifts degeneracy Resonator quality factor power dependence (TLS saturation) coupler Sage et al. JAP 10

15 GETTING STARTED (2012-) DEPOSITION, FABRICATION MEASUREMENT

16 Deposition tools Fast turnaround, flexibility, reliability, good control Deposition, cleaning, oxidation Al-AlO x -Al tunnel junctions Sputter tool Plasma 1 Al, Nb, NbN, AlO x resonators Shadow evaporation tool Plassys E-beam evaporator Al-shadow evaporated junctions Ti/Au markers, AuPd resistors Sputter tool Plasma 2 Nitride superconductors Heating stage (500 C)

17 DFG Center for Functional Nanostructures Nanostructure Service Laboratory

18 Schematic fabrication 1. Design software 2. Film deposition, 3. E-beam markers optical litho, etch optical litho 3 wafer (Si, Al2O3) Inductor, capacitor, flux bias (1 µm+ feature sizes) Markers (crosses etc.) 4. Dice into 5. E-beam litho, Al-AlO x - 6. Dice into 20x20 mm 2 Al shadow evaporation 5x5mm 2 Get 6 chips w/ same designs Dolan bridges, Tunnel junctions, Get 9 chips w/ different designs

19 12 qubit chip cavemon Flux bias Qubit Transmission line 150 µm Readout resonator

20 400 mm cold plate 3 He/ 4 He dilution refrigerator 18 coax lines, 24 filtered DC lines 6 HEMTs (2x LNF) 2-port, 4-port microwave switches, circulators, filters, infrared shield Fits 9 samples Multi-tone spectroscopy, flux bias, time domain measurements

21 FIRST RESULTS

22 Josephson tunnel junctions Al-AlO x -Al junctions Ultra-small shadow evaporated (aka Dolan JJs) Micron-sized cross JJs, evaporated and sputtered Dolan JJ Current-voltage characteristic at 300mK 200 nm 10 mm F Cross JJ

23 Microwave resonators Internal quality factor versus power NbN λ resonator Al, Nb, NbN, and AlO x resonators quality factors photon, power Designs: Geometric, lumped element, spiral, coplanar waveguide, microstrip

24 Microstrip transmon qubits (non-tunable and tunable) 10 mm 100 mm F Flux F to qubit resonator response Qubit spectroscopy Increase drive power higher level visible ½(0 2) Braumüller, MA thesis 13

25 The team Egor Kiselev Kai Kleindienst Marcel Langer Markus Neuwirth Alexander Stehli Tobias Bier Joel Cramer Amadeus Dieter Peter Fehlner Marco Pfirrmann Steffen Schlör Jochen Braumüller Hannes Rotzinger Saskia Meißner Sasha Lukashenko Sebastian Skacel Michael Meyer Ping Yang Roland Jehle Lucas Radtke Gernot Goll Alexey Ustinov Georg Weiß Thanks for your attention