A cryogenic electro-optic interconnect for superconducting devices

Abstract

Encoding information onto optical fields using electro-optical modulation is the backbone of modern telecommunication networks, offering vast bandwidth and low-loss transport via optical fibers [1]. For these reasons, optical fibers are also replacing electrical cables for short range communications within data centers [2]. Compared to electrical coaxial cables, optical fibers also introduce two orders of magnitude smaller heat load from room to milli-Kelvin temperatures, making optical interconnects based on electro-optical modulation an attractive candidate for interfacing superconducting quantum circuits [3-5] and hybrid superconducting devices [6]. Yet, little is known about optical modulation at cryogenic temperatures. Here we demonstrate a proof-of-principle cryogenic electro-optical interconnect, showing that currently employed Ti-doped lithium niobate phase modulators [7] are compatible with operation down to 800 mK-below the typical operation temperature of conventional microwave amplifiers based on high electron mobility transistors (HEMTs) [8, 9]-and maintain their room temperature Pockels coefficient. We utilize cryogenic electro-optical modulation to perform spectroscopy of a superconducting circuit optomechanical system, measuring optomechanically induced transparency (OMIT) [10][11][12][13]. In addition, we encode thermomechanical sidebands from the microwave domain onto an optical signal processed at room temperature. Although the currently achieved noise figure is significantly higher than that of a typical HEMT, substantial noise reduction should be attainable by harnessing

Cryogenic electro-optic modulation in titanium in-diffused lithium niobate waveguides

“…Furthermore, superconducting single photon detectors such as transition edge sensors [22] and SNSPDs have been integrated in lithium niobate [23,24,25,26,27,28,17]. Finally, lithium niobate offers a large electro-optic effect for optical modulation, which is also functional at cryogenic temperatures [29,30,31,32,33]. [29,30], independently demonstrated a directional coupler in lithium niobate at low temperature for the first time.…”

“…A cryogenic phase modulator was used in Refs. [33,17] to read out a superconducting device. Polarisation conversion under cryogenic conditions was recently demonstrated by our group [32].…”

Control and readout of a superconducting qubit using a photonic link

“…The development of quantum-coherent interconnects, capable of sharing fragile quantum states between processors in separate cryostats, has attracted large efforts but remains a longstanding challenge [11][12][13][14]. Concurrently, innovations in classical interconnects aim at reducing the heat load associated with interfacing with the quantum processor arXiv:2009.01167v1 [quant-ph] 2 Sep 2020 2 [15][16][17][18][19][20]. Indeed, a low-power cryogenic link, capable of delivering classical signals suitable for high fidelity qubit operation, could be instrumental in building a large-scale quantum computer.…”

“…This work highlights the benefits of mature opto-electronic technology for quantum applications and will only be enhanced by further optimization of hardware and protocols specifically tailored for cryogenic operation. Combined with photonic methods for transmitting the qubit state information to room temperature on optical fiber [19,20], we envision a fully photonic interface with a superconducting quantum processor. This promising technology provides a path toward scaling superconducting quantum processors to an unprecedented number of quantum bits, enabling many of the longstanding promises of the quantum revolution.…”

Gigahertz free-space electro-optic modulators based on Mie resonances

“…Today, most demonstrations target fiber applications and foster photonic integrated platforms [14,15] such as silicon-on-insulator technologies, where a low optical loss and a high transduction efficiency have been achieved. These two figures of merit are key for a wide range of applications, and are especially crucial for quantum applications [16,17]. Waveguide-based electro-optic modulators have a size on the order of few tens to few hundreds of wavelengths (such as e.g.…”