Engineering the microwave to infrared noise photon flux for superconducting quantum systems

Abstract

Electromagnetic filtering is essential for the coherent control, operation and readout of superconducting quantum circuits at milliKelvin temperatures. The suppression of spurious modes around transition frequencies of a few GHz is well understood and mainly achieved by on-chip and package considerations. Noise photons of higher frequencies – beyond the pair-breaking energies – cause decoherence and require spectral engineering before reaching the packaged quantum chip. The external wires that pass into the refrigerator and go down to the quantum circuit provide a direct path for these photons. This article contains quantitative analysis and experimental data for the noise photon flux through coaxial, filtered wiring. The attenuation of the coaxial cable at room temperature and the noise photon flux estimates for typical wiring configurations are provided. Compact cryogenic microwave low-pass filters with CR-110 and Esorb-230 absorptive dielectric fillings are presented along with experimental data at room and cryogenic temperatures up to 70 GHz. Filter cut-off frequencies between 1 to 10 GHz are set by the filter length, and the roll-off is material dependent. The relative dielectric permittivity and magnetic permeability for the Esorb-230 material in the pair-breaking frequency range of 75 to 110 GHz are measured, and the filter properties in this frequency range are calculated. The estimated dramatic suppression of the noise photon flux due to the filter proves its usefulness for experiments with superconducting quantum systems.

Control on the Sensor Coherence of Transmon Superconducting Qubit via the Gradient Descent Algorithm

“…The principal scheme for Ramsey fringes interferometry of external magnetic field is presented in Fig. 2 (let us call it the Danilin-Nugent-Weides, or DNW protocol) [6]. This scheme consists of the following principal parts:…”

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Scalable Cryoelectronics for Superconducting Qubit Control and Readout

“…Moreover, the high‐frequency interconnects from the room temperature (300 K) electronics to the quantum processor at cryogenic temperature (<1 K) should be minimized, also to minimize the need for filtering of infrared photons. [ 18 ] Ideally, the electronics need to reside with the quantum processor at cryogenic temperatures to address the obstacles mentioned above; however, due to the dilution refrigerator's current cooling limitation, as a first step, cryogenic electronics can be placed close to the quantum processor with short high‐frequency interconnects and using multiplexed circuit architecture. Efficient cryogenic circuits and systems can only be designed if reliable cryogenic CMOS (CryoCMOS) device models are available.…”

Insulation characteristics of polyimide film used in liquid nitrogen of compact HTS transformers

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