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Journal of Optical Technology

Design and performance analysis of a deterministic iSWAP gate using a resonator as a coupler

Amit Kumar Sharma, Ritu Sharma

Published Nov 1, 2021• 0 citations
Publisher

Abstract

In this paper, quantum process tomography of the designed photonic-qubit-based deterministic iSWAP gate has been done and compared with the ideal iSWAP gate. The gate is designed and simulated using a resonator as a coupler. The performance (fidelity and concurrence) of the designed iSWAP gate has been analytically investigated. The effect of cavity parameters (coupling strength and cavity mode decay rate) on performance of the designed iSWAP gate has been observed. A maximum fidelity of 47.06% is obtained at a coupling strength of 0.02 and cavity mode decay rate of 0.0005, and a maximum concurrence of 0.474 is obtained at a coupling strength of 0.02 and cavity mode decay rate of 0. The research work reported in this paper can be used for further investigation and implementation of quantum information processing systems.

DOI
10.1364/jot.88.000666

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In this paper, quantum process tomography of the designed photonic-qubit-based deterministic iSWAP gate has been done and compared with the ideal iSWAP gate. The gate is designed and simulated using a resonator as a coupler. The performance (fidelity and concurrence) of the designed iSWAP gate has been analytically investigated. The effect of cavity parameters (coupling strength and cavity mode decay rate) on performance of the designed iSWAP gate has been observed. A maximum fidelity of 47.06% is obtained at a coupling strength of 0.02 and cavity mode decay rate of 0.0005, and a maximum concurrence of 0.474 is obtained at a coupling strength of 0.02 and cavity mode decay rate of 0. The research work reported in this paper can be used for further investigation and implementation of quantum information processing systems.
Abstract A Quantum dot implanted within double-sided optical microcavity is explained and established as a critical component for all optical-based quantum internets. Due to the duality as the photonic quantum transistor and gate, the QD cavity system presents a sturdy base for the future photonic quantum network. With the help of the analytical investigation and review presented in this paper, a quantum dot cavity unit can be developed for implementing deterministic quantum gates and transistors. The maximum fidelity observed for quantum diode, router, and storage is 95.24%, 62.06%, and 90.42% without considering a noisy environment, respectively, and 62.12%, 60.36%, and 43.66% under a noisy environment, respectively. Fidelity is also calculated with varying coupling conditions (strong and weak coupling), and optimized cavity parameters are calculated. The paper also reports the work done by various researchers till date.
Abstract Based on a cavity QED framework, we theoretically describe a universal set of logic gates which are implemented by passing a multi-level atom initially in its ground state through a multi-mode cavity. The qubits are encoded on the cavity modes and the atom plays the role of an ancilla which will not be entangled with the final result of a gate operation. We apply the multiphoton resonance theory of Shore to develop effective two- and three-level Hamiltonians, so that the proper values for detunings, coupling coefficients, and interaction times for gate operations can be determined. This enables us to examine a faster iSWAP gate than our previous study and to examine numerically the effects of decoherence on both the iSWAP gate and our previously presented Fredkin gate which used the same multi-mode approach. We also present results that show how conditional measurements of the ancilla atom can improve gate fidelities in these cases.
Entangling operations are at the heart of all approaches to quantum information processing. Parametric gates, in particular, offer a versatile solution to strongly couple off-resonant superconducting qubits with suppressed parasitic crosstalk to spectator qubits due to frequency-selective activation. In this work, we demonstrate a parametric iSWAP gate between two transmon qubits using the recently developed double transmon coupler (DTC). The DTC supports robust internally-defined cancellation point (``off'' state) for static interactions, while simultaneously mediating a fast parametric coupling between data qubits that can be deployed for high-fidelity two-qubit operations. We use robust phase estimation to calibrate non-commuting error terms in the parametric iSWAP gate, and achieve a 99.827% gate fidelity in 40ns without any numerical optimization. The circuit architecture and calibration techniques developed here are extensible to other gate implementations and qubit modalities, paving the way towards resource-efficient quantum information processing.
Abstract Resonators in circuit quantum electrodynamics systems naturally carry multiple modes, which may have non-negligible influence on qubit parameters and device performance. While new theories and techniques are under investigation to deal with the multi-mode effects in circuit quantum electrodynamics systems, novel engineering designs are also proposed featuring multi-mode resonators to achieve enhanced functionalities of superconducting quantum processors. In this work, multi-mode bus coupling architecture is proposed, in which superconducting qubits are coupled to multiple bus resonators to gain larger coupling strength. Application of multi-mode bus coupler can help improve iSWAP gate fidelity and gate speed beyond the limit of single-mode scenario. The proposed multi-mode bus coupling architecture is compatible with a scalable variation of the traditional bus coupling architecture. It opens up new possibilities for realization of scalable superconducting quantum computation with circuit quantum electrodynamics systems.
Resonators in circuit quantum electrodynamics systems naturally carry multiple modes, which may have non-negligible influence on qubit parameters and device performance. While new theories and techniques are under investigation to deal with the multi-mode effects in circuit quantum electrodynamics systems, researchers have proposed novel engineering designs featuring multi-mode resonators to achieve enhanced functionalities of superconducting quantum processors. Here, we propose multi-mode bus coupling architecture, in which superconducting qubits are coupled to multiple bus resonators to gain larger coupling strength. Applications of multi-mode bus couplers can be helpful for improving iSWAP gate fidelity and gate speed beyond the limit of single-mode scenario. The proposed multi-mode bus coupling architecture is compatible with a scalable variation of the traditional bus coupling architecture. It opens up new possibilities for realization of scalable superconducting quantum computation with circuit quantum electrodynamics systems.
A variety of photon-mediated operations are critical to the realization of scalable quantum information processing platforms and their accurate characterization is essential for the identification of optimal regimes and their experimental realizations. Such light-matter interactions are often studied with a broad variety of analytical and computational methods that are constrained by approximation techniques or by computational scaling. Quantum processors present a new avenue to address these challenges. We consider the case of cavity mediated two-qubit gates. To investigate quantum state transfer between the qubits, we implement simulations with quantum circuits that are able to reliably track the dynamics of the system. Our quantum algorithm, compatible with NISQ (Noisy Intermediate Scale Quantum) era systems, allows us to map out the fidelity of the state transfer operation between qubits as a function of a broad range of system parameters including the respective detunings between the qubits and the cavity, the damping factor of the cavity, and the respective couplings between the qubits and the cavity. The algorithm provides a robust and intuitive solution, alongside a satisfactory agreement with analytical solutions or classical simulation algorithms in their respective regimes of validity. It allows us to identify under-explored regimes of optimal performance, relevant for heterogeneous quantum platforms, where the two-qubit gate can be rather effective between far-detuned qubits that are neither resonant with each other nor with the cavity. Besides its present application, the method introduced in the current paper can be efficiently used in otherwise untractable variations of the model and in various efforts to simulate and optimize photon-mediated two-qubit gates and other relevant operations in quantum information processing.