Quantum computers have surpassed their classical predecessors in terms of speed and capacity. According to the International Business Machines Corporation (IBM), quantum computing harnesses the laws of quantum mechanics to solve too complex problems for classical computers.
Additionally, quantum computers have qubits or superconducting circuits that exist in an infinite combination of binary states. However, they must be on the same wavelength that is achieved at the cost of their size. As of now, they are still measured in millimeters and are even bigger than the transistors used in classical computers that are now shrunk in nanometer scales.
The FMN Laboratory team is assembling the cryogenic part of the quantum computer, which provides cooling of superconducting processors to almost absolute zero (-273.1°C). The chips of such processors are based on superconducting qubits and coplanar resonators operating at microwave frequencies. The qubit (“quantum bit”) – the driving force of a quantum computer – exhibits its unique properties only in conditions of absolute zero temperature and complete protection against external influences provided by the dilution cryostat.
Qubits: The Building Blocks of Quantum Computing
Qubits or also known as the quantum bit is the quantum mechanical version of a classical bit. As Quantum Inspire explains, quantum computing encodes information in qubits, while classical computing encodes information in bits.
There are many physical applications of qubits possible, such as polarizations o a photon, a superconducting Transmon qubit, and the nuclear spin states of an atom or an electron.
However, their size remains the main concern for scientists as they are still too big for integrating them into technologies. When combined into larger and larger circuit chips, they make a big physical footprint. That means quantum computers take up a lot of physical space, which cannot be carried in backpacks or worn like watches.
That is why researchers from Columbia University School of Engineering and Applied Science have looked for a way to shrink qubits but at the same time maintain their performance. They noted that the field would need a new way to build the capacitors that store the energy that powers the qubits.
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Shrinking Qubits Using Atom-Thin Materials
In the study, titled "Miniaturizing Transmon Qubits Using van der Waals Materials" published in Nano Letters, researchers demonstrated a superconducting capacitor that was built with atom-sized 2D materials.
Phys.org reported that researchers stuffed an insulating layer of boron nitride between two charged plates of superconducting niobium diselenide, which are all just as big as an atom held together by the weak interaction between electrons called van der Waals forces. Then they combined their capacitors with aluminum circuits to create a two qubit-chip measuring 109 square micrometers and 34 nanometers thick, which is 1,000 times smaller than the ones produced under conventional approaches.
When cooled at absolute zero, qubits still have the same wavelength and the team noticed that the two qubits become entangled and act as one unit for only 1 microsecond. This phenomenon is called quantum coherence in which the quantum state of a qubit is manipulated and readout through electrical pulses.
Researchers said that the findings suggest this is only the first step in exploring the use of 2D materials in quantum computing as they may hold the key to making quantum computers possible. Earlier research from MIT also took advantage of niobium diselenide and boron nitride in building parallel-plate capacitors for qubits that have longer coherence times of up to 25 microseconds
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