"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates"
"uuid:2a9b2e13-8e1e-4d09-a2b3-33a6aeff44bd","http://resolver.tudelft.nl/uuid:2a9b2e13-8e1e-4d09-a2b3-33a6aeff44bd","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)","","2019","Variational quantum eigensolvers offer a small-scale 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 ground-state 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 single-excitation subspace respecting the parity symmetry of the qubit-mapped Hamiltonian. Symmetry verification improves the energy and state estimates by mitigating the effects of qubit relaxation and residual qubit excitation, which violate the symmetry. A full-density-matrix 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 ground-state energy.","","en","journal article","","","","","","","","","","","","","",""
"uuid:827a9922-315d-48b8-933e-2ca299eaedf5","http://resolver.tudelft.nl/uuid:827a9922-315d-48b8-933e-2ca299eaedf5","Fast, High-Fidelity Conditional-Phase Gate Exploiting Leakage Interference in Weakly Anharmonic Superconducting Qubits","Rol, 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 Jülich GmbH); DiCarlo, L. (TU Delft DiCarlo Lab; TU Delft QN/DiCarlo Lab; TU Delft QuTech; Kavli institute of nanoscience Delft)","","2019","Conditional-phase (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 built-in echo to enhance fidelity (99.1%) and is robust to long-timescale distortion in the flux-control line, ensuring repeatability. Numerical simulations matching experiment show that fidelity is limited by high-frequency dephasing and leakage by short-timescale distortion.","quantum benchmarking; quantum control; quantum gates; superconducting qubits","en","journal article","","","","","","","","","","","","","",""
"uuid:40d9eee9-d6b4-4722-b3eb-3b0637904b2f","http://resolver.tudelft.nl/uuid:40d9eee9-d6b4-4722-b3eb-3b0637904b2f","General method for extracting the quantum efficiency of dispersive qubit readout in circuit QED","Bultink, 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); Haandbæk, 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)","","2018","We present and demonstrate a general three-step method for extracting the quantum efficiency of dispersive qubit readout in circuit QED. We use active depletion of post-measurement photons and optimal integration weight functions on two quadratures to maximize the signal-to-noise ratio of the non-steady-state 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 traveling-wave parametric amplifier and to quantify different noise contributions in the readout amplification chain.","","en","journal article","","","","","","Accepted Author Manuscript","","","QuTech","","DiCarlo Lab","","",""
"uuid:52a3b5fd-c479-43d2-8b5b-67b517730857","http://resolver.tudelft.nl/uuid:52a3b5fd-c479-43d2-8b5b-67b517730857","A Microarchitecture for a Superconducting Quantum Processor","Fu, 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); García 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)","","2018","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 non-deterministic timing into event trigger with precise timing. QuMA is validated by several single-qubit experiments on a superconducting qubit.","Emerging Technologies; Hardware; Quantum Computing","en","journal article","","","","","","","","","QuTech","Quantum & Computer Engineering","Computer Engineering","","",""
"uuid:ceeb2c94-47aa-4477-aba7-4bf0d568556f","http://resolver.tudelft.nl/uuid:ceeb2c94-47aa-4477-aba7-4bf0d568556f","An experimental microarchitecture for a superconducting qantum processor","Fu, 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); García 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)","","2017","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 high-level programming languages and compilers to describe and optimize quantum algorithms, and building reliable low-level 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 quantum-classical mixed code for a superconducting quantum processor. The microarchitecture is based on three core elements: (i) a codeword-based event control scheme, (ii) queue-based 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 gate-characterization experiment on a transmon qubit.","Quantum (micro-) architecture; Quantum instruction set architecture (QISA); QuMA; QuMIS; Superconducting quantum processor; OA-Fund TU Delft","en","conference paper","IEEE Computer Society","","","","","","","","","Quantum & Computer Engineering","Computer Engineering","","",""
"uuid:1a29b8e6-a89c-43e1-814f-ae53b04266e4","http://resolver.tudelft.nl/uuid:1a29b8e6-a89c-43e1-814f-ae53b04266e4","Restless Tuneup of High-Fidelity Qubit Gates","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); 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); Lüthi, 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)","","2017","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 Nelder-Mead optimization from real-time 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 gate-set tomography. The adjustable sensitivity of the cost function allows the detection of fractional changes in the gate error with a nearly constant signal-to-noise ratio. The restless concept demonstrated can be readily extended to the tuneup of two-qubit gates and measurement operations.","Research Areas","en","journal article","","","","","","","","","","","","","",""
"uuid:5f614893-de32-4be2-b7b2-55d5dba1ef01","http://resolver.tudelft.nl/uuid:5f614893-de32-4be2-b7b2-55d5dba1ef01","Active Resonator Reset in the Nonlinear Dispersive Regime of Circuit QED","Bultink, C.C. (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)","","2016","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 quantum-parity 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 1-μs cycle time.","Electronics; Quantum Information","en","journal article","","","","","","","","","","","","","",""
"uuid:35f9112e-bf69-433f-92aa-0843cdfc7c7e","http://resolver.tudelft.nl/uuid:35f9112e-bf69-433f-92aa-0843cdfc7c7e","Millisecond charge-parity fluctuations and induced decoherence in a superconducting transmon qubit","Riste, D.; Bultink, C.C.; Tiggelman, M.J.; Schouten, R.N.; Lehnert, K.W.; DiCarlo, L.","","2013","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 transmon-type charge qubits. Here, by integrating recent developments in high-fidelity qubit readout and feedback control in circuit quantum electrodynamics, we transform a state-of-the-art transmon into its own real-time charge-parity 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.","physical sciences; applied physics; nanotechnology","en","journal article","Nature Publishing Group","","","","","","","","Applied Sciences","QN/Quantum Nanoscience","","","",""
"uuid:76b4612a-0725-4d97-bf20-c58bcb3b01ea","http://resolver.tudelft.nl/uuid:76b4612a-0725-4d97-bf20-c58bcb3b01ea","Feedback Control of a Solid-State Qubit Using High-Fidelity Projective Measurement","Riste, D.; Bultink, C.C.; Lehnert, K.W.; DiCarlo, L.","","2012","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 closed-loop qubit control is necessary for measurement-based protocols such as quantum error correction and teleportation.","","en","journal article","American Physical Society","","","","","","","","Applied Sciences","QN/Quantum Nanoscience","","","",""