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Similar to APS March Meeting - Superconducting qubit devices: fabrication suite
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APS March Meeting - Superconducting qubit devices: fabrication suite
- 1. Kok Wai Chan Team Leader in Device Fabrication kokwai@meetiqm.com Superconducting qubit devices: fabrication suite K. W. Chan, T. Li, W. Liu, J. Heinsoo, V. A. Sevriuk, M. Jenei, F. Marxer, C. Ockeloen- Korppi, J. Tuorila, J. Hassel, J. Vartiainen, K. Y. Tan, J. Goetz, and M. Möttönen IQM Finland Oy, Espoo Finland
- 2. IQM in brief • Founded in 2018, located in Espoo, Finland • Seed funding round, 11.5 M€ secured in July 2019 • > 30 employees • Superconducting qubit design and fabrication • IP: QCR for fast qubit reset and readout • Manufacture in-house microwave electronics to control and readout a quantum processor 2Fast Lane for Quantum Computers QCR = quantum circuit refrigerator
- 3. Outline 3 ➢Transmon qubit ➢Fabrication of microwave resonators and 1-qubit gate device ➢Microwave resonators ➢Single qubit gate with on-chip airbridges ➢Other projects ➢Acknowledgement Fast Lane for Quantum Computers
- 4. Transmon Qubit 4Fast Lane for Quantum Computers • Qubit is a two level system. • ۧ|0 and ۧ|1 state represented by the absence and presence of a single (microwave) photon in the resonator, respectively • Control of states via microwave drive • Ultra-low temperature to reach ۧ|0 state 𝐶 𝐿 Classical 𝐿𝐶-oscillator microwave photon 𝐶coupling ℏ𝜔o ℏ = reduced Planck’s constant, 𝜔0 = 2𝜋𝑓0, 𝑓0 = fundemental frequency of resonator/transmon 𝐶 Non-linear inductor 𝐿(𝑛) Transmon microwave photon 𝐶coupling ℏ𝜔o EJ > EC Ec = e2/2Csum Csum (geometry) • Need anharmonicity and less charge dispersion, not to excite other transitions. • Anharmonicity (non-linear inductor) implementation –> Josephson junction (JJ) • JJ is inherently lossless, good for qubit lifetime. [1] P. Krantz et al., Appl. Phys. Rev. 6, 021318 (2019)
- 5. Transmon Qubit 5Fast Lane for Quantum Computers 𝐶 Non-linear inductor 𝐿(𝑛) Transmon microwave photon 𝐶coupling 𝐶 𝐿 Readout resonator 𝐶κ XY drive SQUID SQUID = superconducting quantum interference device • Actual implementation includes a “dispersive” readout resonator • Minimise qubit perturbation, no energy exchange • Readout resonator 𝑓0 changes according to qubit state
- 6. Fabrication - Transmon Qubit 6Fast Lane for Quantum Computers • Start with a bare ultra high resistivity silicon wafer • Sputter Nb (TC > 7K) • Resist coating • Resist patterning (TL + Resonators) • Resist development • Etch Nb film • Clean / remove resist • Fabricate Al SIS junctions (Dolan bridge) • Fabricate Al airbridges TL = transmission line, PECVD = plasma-enhanced chemical vapour deposition, Nb= niobium, Al = aluminium SIS = superconducting-insulator-superconducting
- 7. Microwave Resonators 7Fast Lane for Quantum Computers Photograph: Multiplexed 18 resonators Qubit lifetime, T1 Qtot = f0/Df-3dB At single photon level f0,1 f0,18 f0,1 f0,18 T1 Q / wge T1= coherence time
- 8. Microwave Resonators 8Fast Lane for Quantum Computers Photograph: Multiplexed 18 resonators Measured internal quality factor < Qi > > 1e6 Qi > 2e6 Totalqualityfactor,𝑸𝐭𝐨𝐭 Coupling distance, 𝒅 Coupling quality factor, 𝑸 𝐜 Internal quality factor, 𝑸𝐢 Total quality factor, 𝑸𝐭𝐨𝐭 𝐶κ = coupling capacitance (between transmission line and resonator) 𝟏 𝑸𝐭𝐨𝐭 = 𝟏 𝑸 𝐜 + 𝟏 𝑸𝐢 Coupling quality factor, 𝑸 𝐜 ∝ 𝟏 𝑪 𝛋 𝟐 ∝ 𝒅 Internal quality factor, 𝑸𝐢 → internal losses Extracting internal quality factor At single photon level Ref: Journal of Applied Physics 104, 113904 (2008)
- 9. 1Qb gate + airbridges 9Fast Lane for Quantum Computers SEM: 1-qubit gate device + airbridges SEM = scanning electron micrograph, T1= coherence time, T2 *= Ramsey dephasing time m-airbridges Measured specifications fres 6.204 GHz fss 5.286 GHz T1 18 ms T2 * 22 ms XY drive transmon readout resonators fres = resonator frequency, fss = qubit frequency at sweet spot
- 10. Other projects – 2-qubit gate 10Fast Lane for Quantum Computers SEM: 2-qubit gate (tunable coupler) Qubit fres (GHz) fss (GHz) T1 (ms) T2 * (ms) 1 6.2877 6.7865 13 23 2 6.4330 !10.8500 2.5 0.3 3 6.5027 7.0600 20 25 Fluxline cross-talk measurement fres = resonator frequency, fss = qubit frequency at sweet spot, ! = not at sweet spot
- 11. Other projects – fast qubit reset 11Fast Lane for Quantum Computers SEM: QCR – fast qubit reset QCR = quantum circuit refrigerator Presented by Johannes on Monday Abstract: A36.00008 : Unconditional reset of superconducting qubits and readout resonators using a quantum-circuit refrigerator [1] V. Sevriuk et al., Appl. Phys. Lett. 115, 082601 (2019) [2] D. Basilewitsch et al., New J. Phys. 21, 093054 (2019)