- Scientists at the National Institute of Standards and Technology (NIST) have developed a device with two superconducting qubits, equivalent to classical logic bits.
- The new device may enable quantum processors with improved versatility and clearer outputs.
What good is a powerful computer if one can not read its output or modify it for various tasks? These are the obstacles quantum computer designers face, but a new device may make them easier to solve.
Scientists at the National Institute of Standards and Technology (NIST) have developed a device featuring two superconducting quantum bits, known as qubits, which are the quantum equivalent of classical computer logic bits. At the core of this innovative approach lies a “toggle switch” device that establishes a connection between the qubits and a circuit called a “readout resonator.” This resonator enables the reading of the qubits’ calculations, allowing for interpreting their output.
By incorporating a programmable toggle switch, the noise levels can be reduced, thereby enhancing the clarity of calculations and displaying accurate results for qubits. The researchers aim to let qubits calculate undisturbed yet readable outputs. This architecture safeguards qubits and enhances measurement fidelity for building quantum processors. Quantum computers, in their early stages, exploit quantum mechanics to tackle tasks beyond classical computers’ capabilities, like simulating complex chemical interactions for drug development. Quantum computer designers face external and internal noise issues affecting quantum circuits due to material defects. This random behaviour introduces errors in qubit calculations. The team’s toggle switch overcomes both problems by blocking the readout resonator’s circuit noise and preventing qubits from interacting when they should remain silent.
Remote-controlled microwave pulses operate the switches between elements, eliminating the need for physical connections in a static architecture. Incorporating more of these toggle switches could lay the foundation for a quantum computer that is more readily programmable and user-friendly. These pulses can also dictate logic operation order, allowing a chip with multiple toggle switches to perform various tasks. Additionally, the toggle switch facilitates simultaneous measurement of both qubits, aiding error detection in quantum computation. The qubits, toggle switch, and readout circuit for the demonstration were constructed using superconducting components, requiring extremely low temperatures.
The toggle switch is crafted from a superconducting quantum interference device, “SQUID.” This device is highly responsive to magnetic fields that traverse its loop, showcasing its exceptional sensitivity. By driving microwave current through a nearby antenna loop, interactions between qubits and the readout resonator can be induced as necessary.
Currently, the team experimented with two qubits and one readout resonator, but they’re developing a design with three qubits and a resonator, with intentions to add more. Further the researchers aim to interconnect these devices, enabling a powerful quantum computer with enough qubits to tackle currently unsolvable problems.
Reference: T. Noh, Z. Xiao, X.Y. Jin, K. Cicak, E. Doucet, J. Aumentado, L.C.G. Govia, L. Ranzani, A. Kamal and R.W. Simmonds. Strong parametric dispersive shifts in a statically decoupled two-qubit cavity QED system. Nature Physics. Published online June 26, 2023. DOI: 10.1038/s41567-023-02107-2