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Calibri 83ffff̙̙3f3fff3f3f33333f33333.TU Delft Repositoryg Xuuidrepository linktitleauthorcontributorpublication yearabstract
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departmentresearch group programmeprojectcoordinates)uuid:827a9922315d48b8933e2ca299eaedf5Dhttp://resolver.tudelft.nl/uuid:827a9922315d48b8933e2ca299eaedf5vFast, HighFidelity ConditionalPhase Gate Exploiting Leakage Interference in Weakly Anharmonic Superconducting QubitsRol, M.A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Battistel, F. (TU Delft FTQC/Terhal Group; TU Delft QuTech); Malinowski, F.K. (TU Delft Kouwenhoven Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Bultink, C.C. (TU Delft General; TU Delft QuTech; Kavli institute of nanoscience Delft); Tarasinski, B.M. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Vollmer, R. (Kavli institute of nanoscience Delft; Student TU Delft); Haider, S.N. (TU Delft QuTech Shared Development; TU Delft QuTech; TNO); Muthusubramanian, N. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Bruno, A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Terhal, B.M. (TU Delft FTQC/Terhal Group; TU Delft Quantum Computing; TU Delft QuTech; Forschungszentrum Jlich GmbH); DiCarlo, L. (TU Delft DiCarlo Lab; TU Delft QN/DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft)WConditionalphase (cz) gates in transmons can be realized by flux pulsing computational states towards resonance with noncomputational ones. We present a 40 ns cz gate based on a bipolar flux pulse suppressing leakage (0.1%) by interference and approaching the speed limit set by exchange coupling. This pulse harnesses a builtin echo to enhance fidelity (99.1%) and is robust to longtimescale distortion in the fluxcontrol line, ensuring repeatability. Numerical simulations matching experiment show that fidelity is limited by highfrequency dephasing and leakage by shorttimescale distortion.Lquantum benchmarking; quantum control; quantum gates; superconducting qubitsenjournal article)uuid:2a9b2e138e1e4d09a2b333a6aeff44bdDhttp://resolver.tudelft.nl/uuid:2a9b2e138e1e4d09a2b333a6aeff44bd\Experimental error mitigation via symmetry verification in a variational quantum eigensolver
Sagastizabal, R.E. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Bonet Monroig, X. (TU Delft DiCarlo Lab; TU Delft QuTech; Leiden University); Singh, Malay (Student TU Delft; Kavli institute of nanoscience Delft); Rol, M.A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Bultink, C.C. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Fu, X. (TU Delft FTQC/Bertels Lab; TU Delft Computer Engineering; TU Delft QuTech; Kavli institute of nanoscience Delft); Ostroukh, V. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Muthusubramanian, N. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Bruno, A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Haider, S.N. (TU Delft QuTech Shared Development; TNO); O'Brien, T.E. (Leiden University); DiCarlo, L. (TU Delft DiCarlo Lab; TU Delft QN/DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft)Variational quantum eigensolvers offer a smallscale testbed to demonstrate the performance of error mitigation techniques with low experimental overhead. We present successful error mitigation by applying the recently proposed symmetry verification technique to the experimental estimation of the groundstate energy and ground state of the hydrogen molecule. A finely adjustable exchange interaction between two qubits in a circuit QED processor efficiently prepares variational ansatz states in the singleexcitation subspace respecting the parity symmetry of the qubitmapped Hamiltonian. Symmetry verification improves the energy and state estima< tes by mitigating the effects of qubit relaxation and residual qubit excitation, which violate the symmetry. A fulldensitymatrix simulation matching the experiment dissects the contribution of these mechanisms from other calibrated error sources. Enforcing positivity of the measured density matrix via scalable convex optimization correlates the energy and state estimate improvements when using symmetry verification, with interesting implications for determining system properties beyond the groundstate energy.)uuid:40d9eee9d6b44722b3eb3b0637904b2fDhttp://resolver.tudelft.nl/uuid:40d9eee9d6b44722b3eb3b0637904b2f_General method for extracting the quantum efficiency of dispersive qubit readout in circuit QEDEBultink, C.C. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Tarasinski, B.M. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Haandbk, N. (Zurich Instruments AG); Poletto, S. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Haider, S.N. (TU Delft General; TU Delft QuTech; TNO); Michalak, D.J. (Intel Labs); Bruno, A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); di Carlo, L. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft)We present and demonstrate a general threestep method for extracting the quantum efficiency of dispersive qubit readout in circuit QED. We use active depletion of postmeasurement photons and optimal integration weight functions on two quadratures to maximize the signaltonoise ratio of the nonsteadystate homodyne measurement. We derive analytically and demonstrate experimentally that the method robustly extracts the quantum efficiency for arbitrary readout conditions in the linear regime. We use the proven method to optimally bias a Josephson travelingwave parametric amplifier and to quantify different noise contributions in the readout amplification chain.Accepted Author ManuscriptQuTechDiCarlo Lab)uuid:52a3b5fdc47943d28b5b67b517730857Dhttp://resolver.tudelft.nl/uuid:52a3b5fdc47943d28b5b67b517730857;A Microarchitecture for a Superconducting Quantum ProcessorIFu, X. (TU Delft Computer Engineering; TU Delft QuTech); Rol, M.A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Bultink, C.C. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); van Someren, J. (TU Delft FTQC/Bertels Lab; TU Delft Computer Engineering; TU Delft QuTech); Khammassi, N. (TU Delft FTQC/Bertels Lab; TU Delft QuTech); Ashraf, I. (TU Delft FTQC/Bertels Lab; TU Delft QuTech); Vermeulen, R.F.L. (TU Delft General; TU Delft QuTech; Kavli institute of nanoscience Delft); de Sterke, J.C. (TU Delft QuTech; Topic Embedded Systems B.V.); Vlothuizen, W.J. (TU Delft General; TU Delft QuTech; Netherlands Organization for Applied Scientific Research); Schouten, R.N. (TU Delft General; TU Delft QuTech; Kavli institute of nanoscience Delft); Garca Almudever, C. (TU Delft Computer Engineering; TU Delft QuTech); di Carlo, L. (TU Delft DiCarlo Lab; TU Delft QN/DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Bertels, K.L.M. (TU Delft FTQC/Bertels Lab; TU Delft Quantum & Computer Engineering; TU Delft QuTech)This article proposes a quantum microarchitecture, QuMA. Flexible programmability of a quantum processor is achieved by multilevel instructions decoding, abstracting analog control into digital control, and translating instruction execution with nondeterministic timing into event trigger with precise timing. QuMA is validated by several singlequbit experiments on a superconducting qubit.2Emerging Technologies; Hardware; Quantum ComputingQuantum & Computer EngineeringComputer Engineering)uuid:ceeb2c9447aa4477aba74bf0d568556fDhttp://resolver.tudelft.nl/uuid:ceeb2c9447aa4477aba74bf0d568556fHAn experimental microarchitecture for a superconducting qantum processorFu, X. (TU Delft Computer Engineering); Rol, M.A. (TU Delft DiCarlo Lab); Bultink, C.C. (TU Delft DiCarlo Lab); van Someren, J.< (TU Delft FTQC/Bertels Lab; TU Delft Computer Engineering); Khammassi, N. (TU Delft FTQC/Bertels Lab); Ashraf, I. (TU Delft FTQC/Bertels Lab); Vermeulen, R.F.L. (TU Delft General); de Sterke, J.C. (TU Delft DiCarlo Lab; Topic Embedded Systems B.V.); Vlothuizen, W.J. (TU Delft General; TNO); Schouten, R.N. (TU Delft General); Garca Almudever, C. (TU Delft Computer Engineering); di Carlo, L. (TU Delft DiCarlo Lab; TU Delft QN/DiCarlo Lab); Bertels, K.L.M. (TU Delft FTQC/Bertels Lab; TU Delft Quantum & Computer Engineering)Quantum computers promise to solve certain problems that are intractable for classical computers, such as factoring large numbers and simulating quantum systems. To date, research in quantum computer engineering has focused primarily at opposite ends of the required system stack: devising highlevel programming languages and compilers to describe and optimize quantum algorithms, and building reliable lowlevel quantum hardware. Relatively little attention has been given to using the compiler output to fully control the operations on experimental quantum processors. Bridging this gap, we propose and build a prototype of a flexible control microarchitecture supporting quantumclassical mixed code for a superconducting quantum processor. The microarchitecture is based on three core elements: (i) a codewordbased event control scheme, (ii) queuebased precise event timing control, and (iii) a flexible multilevel instruction decoding mechanism for control. We design a set of quantum microinstructions that allows flexible control of quantum operations with precise timing. We demonstrate the microarchitecture and microinstruction set by performing a standard gatecharacterization experiment on a transmon qubit.Quantum (micro) architecture; Quantum instruction set architecture (QISA); QuMA; QuMIS; Superconducting quantum processor; OAFund TU Delftconference paperIEEE Computer Society)uuid:1a29b8e6a89c43e1814fae53b04266e4Dhttp://resolver.tudelft.nl/uuid:1a29b8e6a89c43e1814fae53b04266e4,Restless Tuneup of HighFidelity Qubit GatesRol, M.A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Bultink, C.C. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); O'Brien, T.E. (Leiden University); De Jong, S. R. (Student TU Delft; Kavli institute of nanoscience Delft); Theis, L. S. (Saarland University); Fu, X. (TU Delft Computer Engineering); Lthi, F. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Vermeulen, R.F.L. (TU Delft General; TU Delft QuTech; Kavli institute of nanoscience Delft); de Sterke, J.C. (TU Delft DiCarlo Lab; TU Delft QuTech; Topic Embedded Systems B.V.); Bruno, A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Deurloo, D. (TU Delft General; TU Delft QuTech; TNO); Schouten, R.N. (TU Delft General; TU Delft QuTech; Kavli institute of nanoscience Delft); Wilhelm, FK (Saarland University); DiCarlo, L. (TU Delft DiCarlo Lab; TU Delft QN/DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft)We present a tuneup protocol for qubit gates with tenfold speedup over traditional methods reliant on qubit initialization by energy relaxation. This speedup is achieved by constructing a cost function for NelderMead optimization from realtime correlation of nondemolition measurements interleaving gate operations without pause. Applying the protocol on a transmon qubit achieves 0.999 average Clifford fidelity in one minute, as independently verified using randomized benchmarking and gateset tomography. The adjustable sensitivity of the cost function allows the detection of fractional changes in the gate error with a nearly constant signaltonoise ratio. The restless concept demonstrated can be readily extended to the tuneup of twoqubit gates and measurement operations.Research Areas)uuid:5f614893de324be2b7b255d5dba1ef01Dhttp://resolver.tudelft.nl/uuid:5f614893de324be2b7b255d5dba1ef01HActive Resonator Reset in the Nonlinear Dispersive Regime of Circuit QEDDBultink, C.C. <T(TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Rol, M.A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); O'Brien, T.E. (Leiden University); Fu, X. (TU Delft Computer Engineering; TU Delft QuTech); Dickel, C. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Vermeulen, R.F.L. (TU Delft General; TU Delft QuTech; Kavli institute of nanoscience Delft); de Sterke, J.C. (TU Delft DiCarlo Lab; TU Delft QuTech; Topic Embedded Systems B.V.); Bruno, A. (TU Delft DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft); Schouten, R.N. (TU Delft General; TU Delft QuTech; Kavli institute of nanoscience Delft); DiCarlo, L. (TU Delft DiCarlo Lab; TU Delft QN/DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft)We present two pulse schemes to actively deplete measurement photons from a readout resonator in the nonlinear dispersive regime of circuit QED. One method uses digital feedback conditioned on the measurement outcome, while the other is unconditional. In the absence of analytic forms and symmetries to exploit in this nonlinear regime, the depletion pulses are numerically optimized using the Powell method. We speed up photon depletion by more than six inverse resonator linewidths, saving approximately 1650 ns compared to depletion by waiting. We quantify the benefit by emulating an ancilla qubit performing repeated quantumparity checks in a repetition code. Fast depletion increases the mean number of cycles to a spurious error detection event from order 1 to 75 at a 1s cycle time. Electronics; Quantum Information)uuid:35f9112ebf69433f92aa0843cdfc7c7eDhttp://resolver.tudelft.nl/uuid:35f9112ebf69433f92aa0843cdfc7c7ebMillisecond chargeparity fluctuations and induced decoherence in a superconducting transmon qubitURiste, D.; Bultink, C.C.; Tiggelman, M.J.; Schouten, R.N.; Lehnert, K.W.; DiCarlo, L.The tunnelling of quasiparticles across Josephson junctions in superconducting quantum circuits is an intrinsic decoherence mechanism for qubit degrees of freedom. Understanding the limits imposed by quasiparticle tunnelling on qubit relaxation and dephasing is of theoretical and experimental interest, particularly as improved understanding of extrinsic mechanisms has allowed crossing the 100 microsecond mark in transmontype charge qubits. Here, by integrating recent developments in highfidelity qubit readout and feedback control in circuit quantum electrodynamics, we transform a stateoftheart transmon into its own realtime chargeparity detector. We directly measure the tunnelling of quasiparticles across the single junction and isolate the contribution of this tunnelling to qubit relaxation and dephasing, without reliance on theory. The millisecond timescales measured demonstrate that quasiparticle tunnelling does not presently bottleneck transmon qubit coherence, leaving room for yet another order of magnitude increase.2physical sciences; applied physics; nanotechnologyNature Publishing GroupApplied SciencesQN/Quantum Nanoscience)uuid:76b4612a07254d97bf20c58bcb3b01eaDhttp://resolver.tudelft.nl/uuid:76b4612a07254d97bf20c58bcb3b01eaRFeedback Control of a SolidState Qubit Using HighFidelity Projective Measurement4Riste, D.; Bultink, C.C.; Lehnert, K.W.; DiCarlo, L.We demonstrate feedback control of a superconducting transmon qubit using discrete, projective measurement and conditional coherent driving. Feedback realizes a fast and deterministic qubit reset to a target state with 2.4% error averaged over input superposition states, and allows concatenating experiments more than 10 times faster than by passive initialization. This closedloop qubit control is necessary for measurementbased protocols such as quantum error correction and teleportation.American Physical Society
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