Constructing Quantum Networks With Superconducting Nano Devices

 -KRISS develops world's first niobium-based nanoelectromechanical device-

 ▲ Image of nanoelectromechanical systems developed by the KRISS

The Superconducting Quantum System Team at the Korea Research Institute of Standards and Science (KRISS, President Hyun-Min Park) Quantum Technology Institute has successfully developed and verified the characteristics of the world’s first niobium-based superconducting nanoelectromechanical device.

▲ Concept image of superconducting nanoelectromechanical device

 ▲ Electron microscope image of superconducting nanoelectromechanical device

The niobium-based nanoelectromechanical device developed by KRISS researchers can be used at more practical temperatures and magnetic field strengths compared to existing aluminium-based devices. This new technology is expected to be used to realize microwave-to-optical frequency converters for quantum networks, microwave devices for quantum computing, and nanomechanical spin-sensing.

 

In superconducting quantum devices, control and measurement of the quantum states of a superconducting qubit using microwaves at gigahertz(GHz) frequencies. It has been well-known that both aluminium and niobium display superconductivity* at extremely low temperatures.

 

*  Superconductivity: Phenomenon in which substances lose electric resistance when the temperature drops below a certain point. Materials with superconductive properties are called superconductors.

 

Niobium is known to be more versatile, being less influenced by environmental factors such as temperature and magnetic field. However, there was no technology that realizes a free-standing device suspended (nanometer; one billionth of a meter) over the electrode on the substrate with a gap of 100 nm, which is crucial for achieving strong electromechanical interaction. This is because it has been highly challenging to create a nanostructure to overcome strong attraction between molecules at the nanoscale and to control the internal residual stress inside the nanomechancial device.

 

After 2 years of research, the Superconducting Quantum System Team of Quantum Technology Institute at KRISS was able to fabricate the world’s first niobium-based nanoelectromechanical device by controlling the residual stress with optimized process conditions for niobium deposition.

 

? The niobium-based nanoelectromechanical device can be operated at 4 K (Kelvin, 273.15 K in absolute temperature is equivalent to 0 °C), and 0.8 T (Tesla). These far surpasses the operating conditions (1 K, 0.01 T) for existing aluminium-based devices.

 

The KRISS team also succeeded in control of microwave signals using the device. The device was able to reduce microwave transmission more than 1000 times through strong electromechanical interaction.

 

? The development of compact nonreciprocal microwave devices* may be accelerated using the device. Nonreciprocal microwave devices transmit microwave signals in one direction, minimizing the introduction of noise to the device from outside.

*  Nonreciprocal microwave device: Devices that transmit microwave signals only in one direction. Key examples of such devices are microwave isolators and circulators.

 

▲ Senior researcher Jinwoong Cha(left) and principal researcher Junho Suh (right)

is preparing a nanoelectromechanical system.

 

▲ The Superconducting Quantum System Team of the KRISS

(Clockwise from top-left, senior researchers Hakseong Kim, Jinwoong Cha,

principal researcher Junho Suh, post-doc researcher Jihwan Kim,

principal researcher Seung Bo Shim)

KRISS Senior Researcher Jinwoong Cha and Principal Researcher Junho Suh said, “the device will be used to develop a microwave-to-optical frequency converter that could connect remote quantum processor,” and added, “we hope the device will go beyond small-scale quantum networking and eventually contribute to the construction of the quantum internet via which quantum information is transmitted freely between a wide range of quantum systems.”

 

This study, funded by the National Research Foundation, Samsung Science and Technology Foundation and KRISS Key Projects, was published in Nano Letters (IF: 11.238), a leading journal in the field of nanoscience.