scholarly journals Realization of High-Fidelity Controlled-Phase Gates in Extensible Superconducting Qubits Design with a Tunable Coupler

2021 ◽  
Vol 38 (10) ◽  
pp. 100301
Author(s):  
Yangsen Ye ◽  
Sirui Cao ◽  
Yulin Wu ◽  
Xiawei Chen ◽  
Qingling Zhu ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Large Scale ◽  
Quantum Systems ◽  
Superconducting Qubits ◽  
Cross Entropy ◽  
High Fidelity ◽  
Average Fidelity ◽  
Control Error ◽  
Qubit System ◽  
Parasitic Coupling

High-fidelity two-qubit gates are essential for the realization of large-scale quantum computation and simulation. Tunable coupler design is used to reduce the problem of parasitic coupling and frequency crowding in many-qubit systems and thus thought to be advantageous. Here we design an extensible 5-qubit system in which center transmon qubit can couple to every four near-neighboring qubits via a capacitive tunable coupler and experimentally demonstrate high-fidelity controlled-phase (CZ) gate by manipulating central qubit and one near-neighboring qubit. Speckle purity benchmarking and cross entropy benchmarking are used to assess the purity fidelity and the fidelity of the CZ gate. The average purity fidelity of the CZ gate is 99.69±0.04% and the average fidelity of the CZ gate is 99.65±0.04%, which means that the control error is about 0.04%. Our work is helpful for resolving many challenges in implementation of large-scale quantum systems.

scholarly journals Path-optimized nonadiabatic geometric quantum computation on superconducting qubits

2021 ◽  
Author(s):  
Cheng-Yun Ding ◽  
Li-Na Ji ◽  
Tao Chen ◽  
Zheng-Yuan Xue
Keyword(s):  
Quantum Computation ◽  
Large Scale ◽  
Fault Tolerant ◽  
High Fidelity ◽  
Noise Resistance ◽  
Geometric Phases ◽  
Single Qubit ◽  
Phase Gate ◽  
New Perspective ◽  
Geometric Quantum Computation

Abstract Quantum computation based on nonadiabatic geometric phases has attracted a broad range of interests, due to its fast manipulation and inherent noise resistance. However, it is limited to some special evolution paths, and the gate-times are typically longer than conventional dynamical gates, resulting in weakening of robustness and more infidelities of the implemented geometric gates. Here, we propose a path-optimized scheme for geometric quantum computation on superconducting transmon qubits, where high-fidelity and robust universal nonadiabatic geometric gates can be implemented, based on conventional experimental setups. Specifically, we find that, by selecting appropriate evolution paths, the constructed geometric gates can be superior to their corresponding dynamical ones under different local errors. Numerical simulations show that the fidelities for single-qubit geometric Phase, $\pi/8$ and Hadamard gates can be obtained as $99.93\%$, $99.95\%$ and $99.95\%$, respectively. Remarkably, the fidelity for two-qubit control-phase gate can be as high as $99.87\%$. Therefore, our scheme provides a new perspective for geometric quantum computation, making it more promising in the application of large-scale fault-tolerant quantum computation.

scholarly journals Rapid and unconditional parametric reset protocol for tunable superconducting qubits

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yu Zhou ◽  
Zhenxing Zhang ◽  
Zelong Yin ◽  
Sainan Huai ◽  
Xiu Gu ◽  
...  
Keyword(s):  
Excited State ◽  
Quantum Computation ◽  
High Speed ◽  
Quantum Communication ◽  
Single Photon ◽  
Superconducting Qubits ◽  
High Fidelity ◽  
State Population ◽  
Critical Task ◽  
Excited State Population

AbstractQubit initialization is a critical task in quantum computation and communication. Extensive efforts have been made to achieve this with high speed, efficiency and scalability. However, previous approaches have either been measurement-based and required fast feedback, suffered from crosstalk or required sophisticated calibration. Here, we report a fast and high-fidelity reset scheme, avoiding the issues above without any additional chip architecture. By modulating the flux through a transmon qubit, we realize a swap between the qubit and its readout resonator that suppresses the excited state population to 0.08% ± 0.08% within 34 ns (284 ns if photon depletion of the resonator is required). Furthermore, our approach (i) can achieve effective second excited state depletion, (ii) has negligible effects on neighboring qubits, and (iii) offers a way to entangle the qubit with an itinerant single photon, useful in quantum communication applications.

scholarly journals Time-dependent Pancharatnam phases and quantum correlations for coupling superconducting two-qubit system with dissipative environment

2020 ◽  
Vol 50 (4) ◽  
Author(s):  
Liyuan Xue ◽  
Z.S. Wang
Keyword(s):  
Quantum Computation ◽  
Quantum Correlations ◽  
Superconducting Qubits ◽  
Time Dependent ◽  
Mixed States ◽  
Pancharatnam Phase ◽  
Qubit System ◽  
Phonon Number ◽  
Dissipative Environment

Two coupling superconducting qubits are studied for the quantum concurrence, discord, and Pancharatnam phase, for the X and Y states under the dephasing and instantaneous decay environment as well as their couplings. We find that the X and Y states are special mixed states according to the Bloch radius. In general, the larger the environment and phonon number are at the larger region of time, the larger the quantum concurrence and discord are. But we find that the environment correlations are helpful to implement the quantum computation. The Pancharatnam phases provide a way to distinguish the X and Y states.

Strongly correlated quantum walks with a 12-qubit superconducting processor

Science ◽  
2019 ◽  
Vol 364 (6442) ◽  
pp. 753-756 ◽  
Author(s):  
Zhiguang Yan ◽  
Yu-Ran Zhang ◽  
Ming Gong ◽  
Yulin Wu ◽  
Yarui Zheng ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Large Scale ◽  
Quantum Walks ◽  
Superconducting Qubits ◽  
Time Dependent ◽  
Strongly Correlated ◽  
Superconducting Qubit ◽  
Many Body ◽  
Universal Quantum ◽  
Many Body Systems

Quantum walks are the quantum analogs of classical random walks, which allow for the simulation of large-scale quantum many-body systems and the realization of universal quantum computation without time-dependent control. We experimentally demonstrate quantum walks of one and two strongly correlated microwave photons in a one-dimensional array of 12 superconducting qubits with short-range interactions. First, in one-photon quantum walks, we observed the propagation of the density and correlation of the quasiparticle excitation of the superconducting qubit and quantum entanglement between qubit pairs. Second, when implementing two-photon quantum walks by exciting two superconducting qubits, we observed the fermionization of strongly interacting photons from the measured time-dependent long-range anticorrelations, representing the antibunching of photons with attractive interactions. The demonstration of quantum walks on a quantum processor, using superconducting qubits as artificial atoms and tomographic readout, paves the way to quantum simulation of many-body phenomena and universal quantum computation.

scholarly journals Scalable distributed gate-model quantum computers

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Laszlo Gyongyosi ◽  
Sandor Imre
Keyword(s):  
Objective Function ◽  
Quantum Computation ◽  
Large Scale ◽  
Quantum Systems ◽  
Function Evaluation ◽  
Small Scale ◽  
Quantum Computers ◽  
Problem Space ◽  
Near Term ◽  
Quantum Technology

AbstractA scalable model for a distributed quantum computation is a challenging problem due to the complexity of the problem space provided by the diversity of possible quantum systems, from small-scale quantum devices to large-scale quantum computers. Here, we define a model of scalable distributed gate-model quantum computation in near-term quantum systems of the NISQ (noisy intermediate scale quantum) technology era. We prove that the proposed architecture can maximize an objective function of a computational problem in a distributed manner. We study the impacts of decoherence on distributed objective function evaluation.

scholarly journals Flux-based superconducting qubits for quantum computation

2002 ◽  
Vol 372-376 ◽  
pp. 194-200 ◽  
Author(s):  
T.P. Orlando ◽  
S. Lloyd ◽  
L.S. Levitov ◽  
K.K. Berggren ◽  
M.J. Feldman ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Superconducting Qubits

Universal quantum computation with quantum-dot cellular automata in decoherence-free subspace

2008 ◽  
Vol 8 (10) ◽  
pp. 977-985
Author(s):  
Z.-Y. Xu ◽  
M. Feng ◽  
W.-M. Zhang
Keyword(s):  
Cellular Automata ◽  
Quantum Dot ◽  
Quantum Computation ◽  
Two Dimensions ◽  
High Fidelity ◽  
Electron Pairs ◽  
Quantum Dot Cellular Automata ◽  
Single Spin ◽  
Universal Quantum ◽  
Decoherence Free Subspace

We investigate the possibility to have electron-pairs in decoherence-free subspace (DFS), by means of the quantum-dot cellular automata (QCA) and single-spin rotations, to deterministically carry out a universal quantum computation with high-fidelity. We show that our QCA device with electrons tunneling in two dimensions is very suitable for DFS encoding, and argue that our design favors a scalable quantum computation robust to collective dephasing errors.

HoloRoyale: A Large Scale High Fidelity Augmented Reality Game

2018 ◽  
Author(s):  
Damien Hompapas ◽  
Christian Sandor ◽  
Alexander Plopski ◽  
Daniel Saakes ◽  
Dong Hyeok Yun ◽  
...  
Keyword(s):  
Augmented Reality ◽  
Large Scale ◽  
High Fidelity ◽  
Augmented Reality Game
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