Quantum Computing is a diabolically complex technology, with many technical obstacles that affect its development. From these challenges two critical problems stand out: miniaturization and quality of the QBIT.
IBM has adopted the superconductive QUBIT route map of reaching a 1,121 -QUIT processor by 2023, which leads to the expectation that 1,000 qubits with the current QBIT form factor is feasible. However, current approaches will require very large chips (50 millimeters on one side or more) at the scale of small wafers, or the use of chiplets in MulticHip modules. While this approach will work, the goal is to achieve a better path to scalability.
Now researchers in MIT has been able to reduce the size of the qubits And it is done in a way that reduces the interference that occurs between neighboring qubits. MIT researchers have increased the number of superconducts that can be added to a device in a 100 factor.
“We are addressing both miniaturization and quality of Qbit,” he said William OliverThe director of the Quantum Engineering Center In the mit. “Unlike the conventional transistal scale, where only the number really matters, for qubits, large numbers are not enough, they must also be high performance. Sacrifying performance for the Qubit number is not a useful trade in quantum computing. They must go hand in hand.
The key to this great increase in Qbito density and interference reduction is reduced to the use of two -dimensional materials, particularly the 2D insulator of hexagonal boron nitruro (HBN). MIT researchers showed that some HBN atomic monocapas can be stacked to form the insulator in the capacitors of a superconductive qbit.
Like other capacitors, the capacitors in these superconductor circuits take the form of a sandwich in which an insulating material is interspersed between two metal plates. The big difference for these capacitors is that superconductor circuits can work only at extremely low temperatures, less than 0.02 degrees above absolute zero (-273.15 ° C).
Superconductor qubits are measured at temperatures as low as 20 millikelvin in a dilution refrigerator.Nathan Fiske/Mit
In that environment, insulating materials that are available for work, such as PE-CVD silicon oxide or silicon nitruro, have enough defects that are too loss for quantum computing applications. To avoid these material deficiencies, most superconductor circuits use what are called Coplanares capacitors. In these capacitors, the plates are placed laterally with each other, from above the other.
As a result, the intrinsic silicon substrate under the plates and, to a lesser extent, the vacuum above the plates serves as a dielectric condenser. Intrinsic silicon is chemically pure and, therefore, has few defects, and the large size dilutes the electric field in the plate interfaces, all of which leads to a low loss capacitor. The lateral size of each plate in this open -face design ends up being quite large (typically 100 percent micrometers) to achieve the required capacitance.
In an effort to get away from the large lateral configuration, MIT researchers embarked on a search for an insulator that has very few defects and is compatible with superconduct condenser plates.
“We chose to study HBN because it is the most used insulator in the investigation of 2D materials due to its chemical cleaning and inertia,” said Colead Author Joel WangA research scientist in the group of quantum engineering systems of the MIT Research Laboratory for Electronics.
On both sides of the HBN, the MIT researchers used the 2D superconductor material, Niobium dislenoid. One of the most complicated aspects of the manufacture of the capacitors was to work with the niobium desenurus, which oxidizes in seconds when exposed to the air, according to Wang. This requires that the condenser assembly occur in a glove compartment full of argon gas.
While this would apparently complicate the expansion of the production of these capacitors, Wang does not consider this as a limiting factor.
“What determines the quality factor of the condenser are the two interfaces between the two materials,” said Wang. “Once the sandwich is performed, the two interfaces are” sealed “and we do not see any notable degradation over time when exposes to the atmosphere. “
This lack of degradation is due to the fact that about 90 percent of the electric field is contained within the structure of the sandwich, so the oxidation of the outer surface of Niobium’s deelenur no longer plays an important role. Ultimately, this causes the condenser’s footprint to be much smaller, and explains the reduction in cross conversation between neighboring qubits.
“The main challenge to expand manufacturing will be the scale of HBN wafers and 2D superconductors as [niobium diselenide]And how you can make a scale stacking of these films, ”Wang added.
Wang believes that this research has shown that HBN 2D is a good insulating candidate to superconduct qubits. He says that the work on the bases made by the MIT team will serve as a roadmap to use other 2D hybrid materials to build superconductor circuits.
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