Recently, Microsoft announced that the Azure Quantum project team has developed a building block for topological qubits that can generate topological phases and measure topological gaps to quantify phase stability. These technological breakthroughs will facilitate the realization of topological computing, laying the foundation for topological qubit-based computers.
A device used to measure topological gaps, picture from Microsoft
Scientists are currently working on complex chemical and molecular processes to help solve major problems facing human society, such as how to reduce greenhouse gases in the atmosphere, produce better batteries and sustainable energy, increase food production on the land, and reduce water pollution.
Even if traditional computers have enormous computing power, the problems described above are beyond the limits of traditional computers, and it currently takes decades, if not hundreds of millions, of years to solve these problems. However, quantum computers that take advantage of the properties of quantum mechanics are able to achieve large-scale information processing in entirely new ways in the future.
"To make the world sustainable, or to solve the problem of climate change, molecules need to be explored and optimized, which is not possible with today's classical computers, and this is where quantum computers do." Zulfi Alam, vice president of Microsoft Quantum, said, "I believe that we need the power of quantum computing to achieve these [goals]. ”
Microsoft Quantum Cryogenic Cooling System, Image from Microsoft
The quantum industry is currently seeking many different ways to develop qubits. When qubits are kept in optimal condition, quantum computers can theoretically use the properties of quantum mechanics (such as superposition, entanglement, and interference) to solve complex problems with many variables, but no quantum computer has been able to fully achieve such performance.
To build a commercial quantum computer, its qubits must exhibit good performance in three dimensions, including the reliability, speed, and size of the calculations.
But quantum states are extremely fragile and unstable in nature, and because they are difficult to maintain in one state, qubits often fail to perform calculations reliably. When qubits encounter ambient noise such as magnetic fields, information is easily lost, and once errors start to appear, quantum computers have to invest more qubits to correct them.
As a result, the Microsoft team says they've been focusing on developing topological qubits. Because of its built-in protection, it is immune to ambient noise, which means that topological qubit-based computers require far fewer qubits to perform calculations and correct errors than other quantum computers. The team speculates that topological qubits can process information quickly and even hold more than a million qubits on a wafer smaller than a credit card's built-in chip.
Experimenters conduct research at Microsoft's Quantum Materials Lab, picture from Microsoft
Based on two decades of investment and research, the Azure Quantum team designed a device capable of triggering the topological phase of matter from a pair of Majorana zero modes. Such quantum excited states do not usually exist in nature and must be induced under extremely precise conditions. The team developed a process in which semiconductors and superconducting materials are placed in layers onto a single device in a highly precisely controlled manner. At specific magnetic fields and voltages, the device can produce a pair of topological phases of majorana zero-mode, as well as measurable topological gaps.
To establish topological protection, quantum information can be encoded in a pair of physically separated Majorana zero modes. This makes topological qubits more immune to ambient noise. When it encounters an ambient noise, that ambient noise does not interact with or destroy information in the qubit. To obtain quantum information in this mode, it is necessary to observe the combined state of two Majorana zero modes at the same time, and make measurements in a strategic way, both to achieve quantum operations and to establish topological protection for qubits.
For now, the team has built up the ability to maintain quantum phases using Majorana zero-mode and measurable topological gaps, removing the biggest technical barrier to making topological qubits and will help future Microsoft quantum computers use topological qubits to store and compute information.
"Microsoft took this very risky but highly rewarding approach, trying to make a qubit of the highest quality that was theoretically available. But the challenge is that no one has actually seen Majorana zero-mode in real life," said Peter Krogstrup, director of science at Microsoft's Quantum Materials Laboratory, "but now that we've done it, it's very exciting." We will continue to evolve our engineering skills, and now it seems that there is indeed a path to large-scale quantum computing. ”