‘Flip switch’ could help quantum computers reduce noise this new device could lead to many quantum structures with clean surfaces.
What good is a powerful computer if you can’t read its output? Or is it easy to adapt it to perform different functions? People developing quantum computers are facing these challenges, and new devices may make them easier to solve. The device (‘Flip switch’ helps quantum computers reduce noise), introduced by a team of scientists from the National Institute of Standards and Technology (NIST), consists of two giant quantum bits, or qubits, which are the analog of a quantum computer and a computer chip.
The heart of the new design is a “toggle switch” device that connects the qubits to a circuit called a “readout resonator” that can read out the output of the qubits assembly. This switch can be switched to different states to adjust the coupling strength between the qubits and the readout resonator. When there is a disability, these three things are mutually exclusive.
When a switch is turned on to connect the two qubits, they can interact and perform calculations. After the calculation is done, the reverse switch can connect a set of qubits to the readout resonator to retrieve the result. Having a continuous program variable reduces noise, a common problem in quantum computing circuits that makes it difficult for qubits to perform calculations and display their results accurately.
“The goal is to make the qubits excited so that they can compute without distraction, and still be able to read them whenever we want,” said Ray Simmonds, a NIST scientist and one of the authors said the document. “Building this device to help protect qubits promises to improve our ability to perform the high-fidelity measurements required to build quantum information processors from qubits.”
The team, which includes scientists from the University of Massachusetts Lowell, the University of Colorado at Boulder, and Raytheon BBN Technologies, explained their findings in a paper published today in Nature Physics.
Quantum computers, which are still in the early stages of development, will use the amazing properties of quantum mechanics to perform tasks that even our most powerful classical computers find impossible, such as helping in developing new drugs by performing rigorous simulations of chemical interactions.
However, the developers of quantum computers still face many problems. One is that quantum circuits accumulate external or even internal noise, which comes from defects in the components of the computer. This noise is essentially random behavior that can create errors in qubit calculations.
Current qubits are noisy, but that’s not the only problem. Most quantum computer designs have a so-called static architecture, where each active qubit is connected to its neighbors and readable. The patterned wiring that connects the qubits to each other and in retrieving them can expose them to additional noise.
Such vertical structures have another drawback: they cannot be easily adjusted. Qubits in a static structure can perform a few related tasks, but in order for a computer to perform a variety of tasks, it must trade in a different structure and a different qubit structure (Imagine changing your laptop’s chip every time you want to use different software, and then feel the need to keep the chip a little more than perfect, and see why that can be annoying).
This group’s revolutionary approach avoids both of these problems. First, it prevents circuit noise from entering the system through the readout resonator and prevents the qubits from talking to each other when they should be quiet. “This reduces the source of noise in quantum computing,” Simmonds said.
Second, the opening and closing of the switches between the elements that control the train of microwaves that are sent visually, but through the physical connection of static structures. Combining many of these switches could form the basis of a potentially fast quantum computer.
The microwave oven can also set the order and process of the logical work, which means the built-in chip and many changes of the same game can do any work. “It makes the crack into an event,” Simmonds said. “Instead of having a factory entirely on chips, you can make changes through software.”
A final advantage is that the conversion switch can also enable the measurement of two qubits at the same time. This ability to ask two qubits to reveal themselves as a pair is essential for finding quantum anomalies. The qubits in this display, along with the toggle switch and readout circuit, are efficient materials that conduct electricity without resistance and will operate at extreme temperatures.
The converter itself is powered by a quantum interference device, or “SQUID”, which is highly sensitive to the magnetic field passing through its loop. Driving a microwave current through a nearby antenna loop can make the interaction between the qubits and the readout resonator when needed.
At the moment, the team is working with two qubits and a single resonator, but Simmonds said they are supporting a configuration with three qubits and a reader, and plan to add more qubits and resonators. Further research may provide insight into how to combine many of these devices, potentially providing a way to build a powerful quantum computer with enough qubits to solve the kinds of problems that, so far, are insurmountable.
Source: NIST
