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Light-induced microwave noise in superconducting microwave-optical transducers

Mingrui Xu, Chunzhen Li, Yuntao Xu, and Hong X. Tang

Phys. Rev. Applied 21, 014022 – Published 12 January 2024

Abstract

Microwave-to-optical transducers are integral to the future of superconducting quantum computing, as they would enable scaling and long-distance communication of superconducting quantum processors through optical-fiber links. However, optically induced microwave noise poses a significant challenge in achieving quantum transduction between microwave and optical frequencies. In this work, we study light-induced microwave noise in an integrated electro-optical transducer harnessing the Pockels effect of thin-film lithium niobate. We reveal three sources of added noise with distinctive time constants ranging from sub- $100 ns$ to milliseconds. Our results provide insights into the mechanisms and corresponding mitigation strategies for light-induced microwave noise in superconducting microwave-optical transducers and pave the way toward realizing the ultimate goal of quantum transduction.

Received 15 September 2023
Accepted 18 December 2023

DOI:https://doi.org/10.1103/PhysRevApplied.21.014022

Physics Subject Headings (PhySH)

Noise Optoelectronics Quantum information with solid state qubits Quantum interconnects

Superconducting qubits Transducers

Microwave techniques Noise measurements

Quantum Information, Science & TechnologyAtomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Mingrui Xu ^†, Chunzhen Li ^†, Yuntao Xu, and Hong X. Tang ^*

Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520, USA

^*[email protected]
^†These authors contributed equally to this work.

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Vol. 21, Iss. 1 — January 2024

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Figure 1
(a) A false-colored microscopic image of the EO transducer. Two strongly coupled optical racetrack resonators are integrated with a superconducting microwave resonator. The microwave resonator is linked to a coplanar waveguide (CPW, not shown) for both rf coupling and dc biasing. The electrical field direction of the designed microwave mode is marked in the coupling regime. The figure is taken from Ref. [23]. (b) The temporal evolution of $n_{i}^{diff}$ obtained at a pulse peak power of 6 dBm, a pulse width of $5 μ s$ , and a pulse period of 1 ms. The optical drive is turned on and off at approximately $6.6 μ s$ and $11.8 μ s$ . The solid purple line is the extrapolation of $n_{i}^{diff}$ . (c) The heat map shows the time evolution of the noise spectrum, with a pulse peak power of 5 dBm, a pulse width of $5 μ s$ , and a pulse period of 1 ms. (d)(i) and (d)(ii) show snapshots of the power spectral density when the pulsed optical drive is on and off. The data in (d)(i) and (d)(ii) are cross sections of (c), marked in correspondingly colored dashed lines.
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Figure 2
(a) The dynamics of $n_{bg}$ over $30 μ s$ , where the optical drive is turned on and off at approximately $6.6 μ s$ and $11.8 μ s$ as marked. The pulsed drive is configured with different peak powers and the same duty cycle of 0.5%. The inset shows the dynamics of $n_{bg}$ over a time span of 5 ms after the optical drive is turned off. The pulsed drive is configured with a peak power of 0 dBm and a pulse width of $10 μ s$ . The black dashed lines are all horizontal lines as guide to the eye. (b) Time traces of $n_{i, slow, off}$ while the peak power is 0 dBm, the pulse width is $10 μ s$ , and the pulse period is 10 ms. The cyan trace is the experimental data, while the red trace is the fit. (c) The output-noise-power time dynamics with $t_{c} = 30 ns$ . Insets (i) and (ii) are enlarged views of the rise-and-fall edges of (c), where fits to exponential functions are shown in the red curves.
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Figure 3
(a) $n_{bg}$ and $n_{i, slow, off}$ as a function of the average power of the optical drive and $n_{i, fast}$ as a function of the pulse peak power of the optical drive. The orange data points correspond to optical drives with a 0-dBm peak power and a 1-ms pulse period, while the pulse width is swept from $5 μ s$ to $80 μ s$ . The blue data points correspond to optical drives with a 0-dBm peak power and a 10- $μ s$ pulse width, while the pulse period is swept from 0.2 ms to 10 ms. The green data points correspond to optical drives with a 5- $μ s$ pulse width and a 1-ms pulse period, while the pulse peak power is swept from -14 dBm to 11 dBm. The dashed red line is an exponential fit to all the data. The fits show $n_{bg} \approx P_{avg}^{0.82}$ and $n_{i, slow, off} \approx P_{avg}^{0.3}$ and $n_{i, fast} \approx P_{peak}^{0.75}$ . (b) The dependence of $n_{i, fast}$ on the duty cycle of the optical drives. The orange and blue data points correspond to the same pulse configurations as in (a). The red dashed line is the average value of the data. (c) $n_{i, slow, on}$ as a function of the average power of the optical drive. The solid lines are used as visual guides. (d) The dependence of $n_{i}^{diff}$ and its different components on the repetition rate of the optical drives. The pulse peak power is fixed at 0 dBm, the pulse width is $10 μ s$ , and the repetition rate is swept from 100 Hz to 5000 Hz.
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Figure 4
(a) A diagram of the superconducting mode being thermalized through the intrinsic and external coupling channels. (b) The possible locations where the light-induced excessive noise couples to the system.
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Figure 5
The experimental data of $s_{dev}$ and its fit.
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Physical Review Applied

Light-induced microwave noise in superconducting microwave-optical transducers

Mingrui Xu, Chunzhen Li, Yuntao Xu, and Hong X. Tang

Phys. Rev. Applied 21, 014022 – Published 12 January 2024

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