Speeding up qubit control with bipolar single-flux-quantum pulse sequences

Vozhakov, Vsevolod A.; Bastrakova, M. V.; Klenov, N. V.; Satanin, A. M.; Soloviev, I. I.

doi:10.1088/2058-9565/acd9e6

Cited by 8 publications

(4 citation statements)

References 53 publications

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“…We note that for unipolar pulse propagation in a conducting medium formation of the reflected wave occurs. In reality, as the spectral values of susceptibility and conductivity are bound by the relation (15), the low-frequency interval always exists when the inequality of equation ( 17) cannot be satisfied. To observe this reflected pulse, a second-order wave equation, equation (5), was also solved for unipolar pulse propagation in a conducting medium.…”

Section: Unidirectional Model Versus Second-order Wave Equationmentioning

confidence: 99%

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Propagation of electromagnetic pulses with nonzero area in dissipative media

Bogatskaya,

Volkova,

Popov

2023

Laser Phys. Lett.

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The propagation of ultrashort electromagnetic pulses with a nonzero electric area in dielectric and conducting media is studied in the frame of a unidirectional propagation model. General solutions for the electric pulse area are obtained for different types of media with a linear response to the external field. It is shown that the evolution of the electric area of the pulse is dramatically different for conducting and non-conducting media. In the case of dielectrics, where the current induced by an external field arises from the polarization of bound electrons, the electric pulse area is an invariant of pulse propagation in spite of the dissipation process. For media with free charge carriers (plasma or semiconductors), the electric pulse area decreases with time due to Joule heating of the media by the static component of the field.

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Section: Unidirectional Model Versus Second-order Wave Equationmentioning

confidence: 99%

“…The value of this momentum governs the subsequent quantum system dynamics [8,9,11,12]. Another application of unipolar pulses for transferring information from one qubit to another one was discussed in [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Propagation of electromagnetic pulses with nonzero area in dissipative media

Bogatskaya,

Volkova,

Popov

2023

Laser Phys. Lett.

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“…[6] To overcome the bottleneck, rapid single flux quantum (RSFQ) logic circuits [7] integrated with qubits for qubit control and readout are desirable. [8,9] This kind of RSFQ circuits can be called quantum-classical interface (QCI), which was proposed by McDermott et al [10] The theory of RSFQ digital coherent XY control was studied [11][12][13] and the fidelities of single-qubit gate for transmons performed by SFQ pulses were measured to be about 95% [14] and improved to over 98.8% with multichipmodule (MCM) architecture. [9] Two-qubit gates based on SFQ including cross-resonance (CR) gates and controlled-phase (CZ) gates were also studied.…”

Section: Introductionmentioning

confidence: 99%

Simulations of superconducting quantum gates by digital flux tuner for qubits

Geng 耿,

He 何,

Liu 刘

et al. 2024

Chinese Phys. B

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The interconnection bottleneck caused by limitations of cable number, inner space and cooling power of dilution refrigerators has been an outstanding challenge for building scalable superconducting quantum computers with the increasing number of qubits in quantum processors. To surmount such an obstacle, it is desirable to integrate qubits with quantum-classical interface (QCI) circuits based on rapid single flux quantum (RSFQ) circuits. In this work, a digital flux tuner for qubits (DFTQ) is proposed for manipulating flux of qubits as a crucial part of the interface circuit. A schematic diagram of the DFTQ is presented, consisting of a coarse tuning unit and a fine-tuning unit for providing magnetic flux with different precision to qubits. The method of using DFTQ to provide flux for gate operations is discussed from the optimization of circuit design and input signal. To verify the effectiveness of the method, simulations of a single DFTQ and quantum gates including a Z gate and an iSWAP gate with DFTQs are performed for flux-tunable transmons. The quantum process tomography corresponding to the two gates is also carried out to analyze the sources of gate error. The results of tomography show that the gate fidelities independent on initial states of the Z gate and the iSWAP gate are 99.935% and 99.676%, respectively. With DFTQs inside, the QCI would be a powerful tool for building large-scale quantum computers.

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“…Digital coherent XY control based on SFQ pulses to transmon qubits was proposed [5], and the fidelities of digital single-qubit gates were measured to be about 95% [6]. Methods of optimization of SFQ pulse sequences for single- [7][8][9] and two-qubit gates, such as cross-resonance and controlled phase (CZ) gates [10][11][12][13], have also been studied.…”

Section: Introductionmentioning

confidence: 99%

Qubit energy tuner based on single flux quantum circuits

Geng,

He,

Huang

et al. 2023

Front. Phys.

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A device called the qubit energy tuner (QET), based on single flux quantum (SFQ) circuits, has been proposed for Z control of superconducting qubits. The QET is created by improving flux digital-to-analog converters (flux DACs). It can set the energy levels or frequencies of qubits, particularly flux-tunable transmons, and perform gate operations requiring Z control. The circuit structure of the QET is elucidated, consisting of an inductor loop and flux bias units for coarse or fine-tuning. The key feature of the QET is analyzed to understand how SFQ pulses change the inductor loop current, which provides external flux for qubits. Three simulations were performed to verify QET functionality. The first simulation verified the responses of the inductor loop current to SFQ pulses, showing a relative deviation of approximately 4.259% between the analytical solutions of the inductor loop current and the solutions from the WRSpice time-domain simulation. The second and third simulations, using QuTip, demonstrated how to perform a Z gate and an iSWAP gate using the QET, respectively, with corresponding fidelities of 99.99884% and 99.93906% for only one gate operation to specific initial states. These simulations indicate that the SFQ-based QET could act as an efficient component of SFQ-based quantum–classical interfaces for digital Z control of large-scale superconducting quantum computers.

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Speeding up qubit control with bipolar single-flux-quantum pulse sequences

Cited by 8 publications

References 53 publications

Propagation of electromagnetic pulses with nonzero area in dissipative media

Propagation of electromagnetic pulses with nonzero area in dissipative media

Simulations of superconducting quantum gates by digital flux tuner for qubits

Qubit energy tuner based on single flux quantum circuits

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