Power/Performance Bits: Mar. 11

Reading qubits faster; capturing carbon; DNA computing.


Reading qubits faster
Researchers at Aalto University and VTT Technical Research Centre of Finland propose a faster way to read information from qubits, the building blocks of quantum computers. Currently, they are extremely sensitive to disruption even in cryogenic environments, holding quantum information for less than a millisecond.

In the method now used to read information from a qubit, a short microwave pulse is applied to the superconducting circuit containing the qubit and then the reflected microwave is measured. After 300 nanoseconds, the state of the qubit can be deduced from the behavior of the reflected signal.

To improve the process, the researchers applied an extra microwave pulse at the same time to the qubit itself, as well as to the circuit attached to the qubit. By using two pulses instead of one, the team was able to make the reflected pulse reveal qubit states substantially faster than when they only applied a single pulse.

“We were able to complete the readout in 300 nanoseconds in our first experiments, but we think that going below 100 nanoseconds is just around the corner,” said Joni Ikonen, a PhD student at Aalto University.

Improving the read speed also improves accuracy, and the team noted a far lower error rate using their method.

Capturing carbon
Scientists at RMIT University, University of New South Wales, University of Wollongong, University of Münster, Queensland University of Technology, North Carolina State University, and Monash University propose a way to turn atmospheric carbon dioxide into solid carbon, making it both easy to store and potentially useful for batteries.

Carbon capture and storage technologies have mainly focused on compressing CO2 into a liquid form, which would be injected into underground storage sites. However, engineering challenges and environmental concerns have limited implementation. Research has been done on turning CO2 into a solid, but thus far it was only possible at extremely high temperatures, a process the researchers said is not commercially viable.

To achieve a room temperature process, the team used an electrochemical technique featuring a liquid metal catalyst containing metallic elemental cerium nanoparticles. Specific surface properties of the catalyst make it extremely efficient at conducting electricity while chemically activating the surface.

The carbon dioxide is dissolved in a beaker filled with an electrolyte liquid and a small amount of the liquid metal, which is then charged with an electrical current. The CO2 slowly converts into solid flakes of carbon, which are naturally detached from the liquid metal surface, allowing the continuous production of carbonaceous solid.

The carbon produced could be used as an electrode, said Dorna Esrafilzadeh, a Vice-Chancellor’s Research Fellow in RMIT’s School of Engineering. “A side benefit of the process is that the carbon can hold electrical charge, becoming a supercapacitor, so it could potentially be used as a component in future vehicles. The process also produces synthetic fuel as a by-product, which could also have industrial applications.”

DNA computing
Researchers at the University of Bristol, Eindhoven University of Technology, and Microsoft Research took a step forward in DNA computing by assembling communities of artificial cells that can chemically communicate and perform molecular computations using entrapped DNA logic gates.

DNA computers, which use programmable interactions between DNA strands to transform DNA inputs into coded outputs, have been proposed for medical biosensing and therapeutics applications, but are slow due to relying on random molecular diffusion in a chemical soup to execute a computational step.

To address this, the team developed semi-permeable capsules containing a diversity of DNA logic gates that together can be used for molecular sensing and computation.

These artificial cell-like entities, called protocells, are capable of sending DNA input and output signals to each other, speeding up molecular computation and protecting the DNA strands inside from degradation. Additionally, the approach makes computational circuits more designable, the team said.

“The ability to chemically communicate between smart artificial cells using DNA logic codes opens up new opportunities at the interface between unconventional computing and life-like microscale systems,” said Professor Stephen Mann, of the University of Bristol’s School of Chemistry. “This should bring molecular control circuits closer to practical applications and provide new insights into how protocells capable of information processing might have operated at the origin of life.”

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