A peculiar physical state in semiconductor layers could advance quantum computing



Milli-electron volt inelastic X-ray scattering structure for many-particle localization in chaotic superlattices. Image credit: Image of the researcher

This can be an advantage in research Quantum computingResearchers have shown that superlattices with embedded nanodots may not be affected by the energy released into the environment.

Scientists around the world are developing new hardware for quantum computers. This is a new type of device that can speed up drug design, financial modeling, and weather forecasting. These computers are based on qubits, which can represent combinations of ones and zeros at the same time. The problem is, ells are moody and decompose to normal dentures when interacting with surrounding substances. But new research in WITH We propose a method to protect these conditions by using a phenomenon called many-body localization (MBL).

In contrast to solids and liquids, MBL is a unique phase of matter that was proposed decades ago. A substance normally reaches thermal equilibrium with its surroundings. This will cool the soup and melt the ice cubes. In MBL, however, objects made up of many strongly interacting objects such as atoms do not achieve such equilibrium. Like sound, heat consists of collective atomic vibrations that can propagate like waves. Objects always have such heat waves inside. However, if there is enough disorder and enough interaction in the arrangement of the atoms, the waves can be trapped and prevent the object from reaching equilibrium.

MBL was demonstrated in the “optical lattice”, which is the arrangement of atoms at very low temperatures, which are held in place with a laser. However, such an adjustment is not practical. MBL has certainly been detected in solid-state systems, but proving the existence of a phase with only very slow temporal dynamics is difficult because researchers can reach equilibrium if they can wait long enough. is. An MIT study showed evidence of MBL in “solid” systems (systems made of semiconductors). Without them, it would have been in equilibrium at the time of surveillance.

“It could open a new chapter in the study of quantum mechanics,” says Raoul Nandokishore, a physicist at the University of Colorado at Boulder, who was not involved in the study.

MIT’s Norman C. Rasmussen Associate Professor Mingda Li led a new study that was published in a recent issue. Nano letter.. Researchers have built a system that includes alternating layers of semiconductor to create 600 layers of fine lasagna (aluminum arsenic followed by gallium arsenide, etc.), each 3 nanometers (one millionth of a millimeter) thick. Bottom. The disorder was created by dispersing “nanodots”, which are 2 nanometer erbium arsenide particles, between the layers. There are three recipes for lasagne or “superlattice”. One has no nano dots, one has nano dots that cover 8% of the area of ​​each layer and the other covers 25%.

According to Li, the team simplified the system by using layers of material instead of bulk material so that heat dissipation across the plane was essentially one-dimensional. And they used nanodots instead of just chemical contaminants to make the disorder worse.

To determine whether these chaotic systems are still in equilibrium, the researchers measured them with X-rays. They used the Argonne National Laboratory’s Advanced Photon Source to irradiate a beam with energies greater than 20,000 electron volts and to decompose the energy difference between the incident X-rays and the energy reflected on the sample surface with energy resolution. Less than 1/1000 electron volt. They shot it at an angle of only 0.5 degrees from parallel to avoid penetrating the superlattice and hitting the board below.

Just as light can be measured in waves and particles, so can heat. The collective atomic heat oscillation in the form of a heat-carrying unit is called a phonon. By interacting with these phonons and measuring how the X-rays reflect off the sample, the experimenter can determine whether the sample is in equilibrium.

Researchers have found that when the superlattice is cold, 30 Kelvin, around -400 degrees Fahrenheit – And it contained nanodots, and this phonon at a certain frequency was out of balance.

“This new quantum phase can open a whole new platform for studying quantum phenomena,” said Li, while more work is still to be done to definitively prove that MBL has been achieved. to say.

To create qubits, some quantum computers use points of matter called quantum dots. Li states that quantum dots, similar to Li nano dots, can act as qubits. Magnets can read and write quantum states, but many-body localization allows them to continue to isolate magnets from heat and other environmental factors.

With regard to heat storage, such superlattices can switch inside and outside the MBL phase through magnetic control of the nanodots. You can temporarily isolate computer parts from heat so that they can dissipate heat when it is not causing damage. Alternatively, heat can be generated and later used to generate electricity.

Conveniently, a nanodot superlattice can be built together with other elements of a computer chip using conventional semiconductor fabrication techniques. According to Li, “it is much more design space than chemical doping and has many uses.”

“We are pleased to see the MBL signature in real material systems,” said Immanuel Bloch, Director of Science at the Max Planck Institute for Quantum Optics. “I think this will help us to better understand the conditions under which MBL is observed in different quantum many-body systems and how a possible coupling to the environment affects the stability of the system. Is a fundamental and important question, and MIT’s experiments are an important step in helping us answer it. “

Reference: “Features of the many-body localization of phonons in a strong and chaotic superlattice” Thanh Nguyen, Nina Andrejevic, Hoi Chun Po, Qichen Song, Yoichiro Tsurimaki, Nathan C. Drucker, Ahmet Alatas, Esen E. Alp, Bogdan M. Leu , Alessandro Cunsolo, Yong Q. Cai, Lijun Wu, Joseph A. Garlow, Yimei Zhu, Hong Lu, Arthur C. Gossard, Alexander A. Puretzky, David B. Geohegan, Shengxi Huang, Mingda Li, July 27, 2021 day Nano letter..
DOI: 10.1021 / acs.nanolett.1c01905

Funding came from the US Department of Energy’s Basic Energy Science Program neutron scattering program.

A peculiar physical state in semiconductor layers could advance quantum computing Source link A peculiar physical state in semiconductor layers could advance quantum computing


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