8 research outputs found
Scalable quantum error correction code on a ring topology of qubits
Quantum error correction is an important ingredient for scalable quantum
computing. Stabilizer codes are one of the most promising and straightforward
ways to correct quantum errors, since they do not require excessive complexity
of physical qubits, are convenient for logical operations, and improve
performance with increasing the involved qubits number. Here, we propose a
linear scalable code of the permutative stabilizers for small distances on the
ring architecture, which takes into account the topological features of the
superconducting platform. We present the way to construct the quantum circuit
of the code and provide numerical simulation that demonstrate the exponential
logical error rate suppression.Comment: 6 pages, 4 figure
High-fidelity transmon coupler activated CCZ gate on fluxonium qubits
The Toffoli gate takes a special place in the quantum information theory. It
opens up a path for efficient implementation of complex quantum algorithms.
Despite tremendous progress of the quantum processors based on the
superconducting qubits, realization of a high-fidelity three-qubit operation is
still a challenging problem. Here, we propose a novel way to perform a
high-fidelity CCZ gate on fluxoniums capacitively connected via a transmon
qubit, activated by a microwave pulse on the coupler. The main advantages of
the approach are relative quickness, simplicity of calibration and significant
suppression of the unwanted longitudinal ZZ interaction. We provide numerical
simulation of 95-ns long gate of higher than 99.99% fidelity with realistic
circuit parameters in the noiseless model and estimate an error of about 0.25%
under the conventional decoherence rates.Comment: 9 pages, 6 figures, 3 table
Demonstration of a parity-time symmetry breaking phase transition using superconducting and trapped-ion qutrits
Scalable quantum computers hold the promise to solve hard computational
problems, such as prime factorization, combinatorial optimization, simulation
of many-body physics, and quantum chemistry. While being key to understanding
many real-world phenomena, simulation of non-conservative quantum dynamics
presents a challenge for unitary quantum computation. In this work, we focus on
simulating non-unitary parity-time symmetric systems, which exhibit a
distinctive symmetry-breaking phase transition as well as other unique features
that have no counterpart in closed systems. We show that a qutrit, a
three-level quantum system, is capable of realizing this non-equilibrium phase
transition. By using two physical platforms - an array of trapped ions and a
superconducting transmon - and by controlling their three energy levels in a
digital manner, we experimentally simulate the parity-time symmetry-breaking
phase transition. Our results indicate the potential advantage of multi-level
(qudit) processors in simulating physical effects, where additional accessible
levels can play the role of a controlled environment.Comment: 14 pages, 9 figure
High fidelity two-qubit gates on fluxoniums using a tunable coupler
Superconducting fluxonium qubits provide a promising alternative to transmons on the path toward large-scale superconductor-based quantum computing due to their better coherence and larger anharmonicity. A major challenge for multi-qubit fluxonium devices is the experimental demonstration of a scalable crosstalk-free multi-qubit architecture with high-fidelity single-qubit and two-qubit gates, single-shot readout, and state initialization. Here, we present a two-qubit fluxonium-based quantum processor with a tunable coupler element. We experimentally demonstrate fSim-type and controlled-Z-gates with 99.55 and 99.23% fidelities, respectively. The residual ZZ interaction is suppressed down to the few kHz levels. Using a galvanically coupled flux control line, we implement high-fidelity single-qubit gates and ground state initialization with a single arbitrary waveform generator channel per qubit.ISSN:2056-638
Coupler Microwave-Activated Controlled-Phase Gate on Fluxonium Qubits
Tunable couplers have recently become one of the most powerful tools for implementing two-qubit gates between superconducting qubits. A tunable coupler typically includes a nonlinear element, such as a superconducting quantum interference device, which is used to tune the resonance frequency of an LC circuit connecting two qubits. Here we propose a complimentary approach where instead of tuning the resonance frequency of the tunable coupler by applying a quasistatic control signal, we excite by microwave the degree of freedom associated with the coupler itself. Because of strong effective longitudinal coupling between the coupler and the qubits, the frequency of this transition strongly depends on the computational state, leading to different phase accumulations in different states. Using this method, we experimentally demonstrate a controlled-Z gate of 44-ns duration on a fluxonium-based quantum processor, obtaining a fidelity of 97.6%±0.4% characterized by cross-entropy benchmarking