Researchers at University College London have developed a new varactor device that can optimize the radiofrequency read-outs of quantum dot devices at ultra-low temperatures, paving the way for more precise and efficient quantum computing systems.
Revolutionizing Quantum Measurements
One of the main barriers to developing quantum computing systems is measuring the sets of coupled qubits in an accurate and rapid way, so many researches are focused on faster and more reliable ways to determine their electrical properties, such as they have charges/spins. Usually, these quantities are measured with radio-frequency resonators that are adjusted through voltage-controlled variable capacitors (varactors).
Have now developed a new kind of varactor using quantum paraelectric materials, at the University College London. The reported device set forth associated with an article in Nature Electronics, provides a tool to tune the radiofrequency cochlea of quantum dot devices at base temperature down to few millikelvin (mK).
A novel varactor for quantum technologies [] co-authored by Mark Buitelaar, describes the breakthrough needed to overcome the limitations of current varactors. “Radio-frequency resonators are used to readout our experiments with quantum devices,” said Buitelaar. ” In order to optimise this readout — e.g. by tuning the frequencies of resonators or their coupling to transmission lines — we needed tunable capacitors (varactors could do), that not only work at a few mK above absolute zero, but which are robust and insensitive to magnetic fields.”
Unlocking the Potential of Quantum Paraelectrics
While varactors have broad use within the semiconductor industry, they are not routinely used in quantum technologies. They just generally don’t work well, if at all, down that cold as seems to be the case with quantum technologies.
In order to tackle this problem, the UCL researchers have created a new type of varactor which they claim will perform well at these low temperatures. Their device is built from two quantum paraelectric materials strontium titanate and potassium tantalate, which have large field tunable permittivity allowing for long-range entanglement at low temperatures.
A varactor is just an electric double layer capacitor which could be used as the basic building block of a memory device based on polarisation, rather than current,” said Buitelaar. Quantum paraelectric materials, of which SrTiO 3 is an example: these never actually freeze but behave in many ways like the high-T c superconductors.
In a test, The researchers examined how their varactors performed and the readings were excellent below -267.1429891 degrees Celsius (6 milikelvins), well-suited for working with quantum dot devices at such low temperatures. The varactors helped us obtain much higher signal-to-noise ratios, hence precision and speed of our measurements,” explained Buitelaar.
Conclusion
This new varactor device found by researchers at University College London is a huge leap by means of quantum computing. The adjustment has the ability to refine quantum measurements with drastic efficiency and precise operations of quantum computing systems by designing radiofrequency read-outs for use at extremely low temperatures in such devices. This means the researchers are not limited to just quantum dots: at the same time, they are examining other possibilities for using this technology with different types of qubit – in semiconducting materials and superconducting systems as well.
