Physicists make leaps in reading qubits using laser light


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Qubits are a building block of quantum computers, but they’re also notoriously poor – they’re hard to observe without erasing their information in the process. Now, new research from the University of Colorado Boulder and the National Institute of Standards and Technology (NIST) could be a leap forward for tackling qubits with a light touch.

In the study, a team of physicists showed that they can read signals from a type of qubit called a superconducting qubit using laser lightwithout destroying a qubit at the same time.

Collection results may be a major step towards building a profile quantum internetResearchers say. Such a network could connect dozens or even hundreds of quantum chips, allowing engineers to solve problems that are inaccessible to even the fastest supercomputers of today. They could also, in theory, use a similar set of tools to send unbreakable codes over long distances.

The study will be published on June 15 in the journal temper natureled by JILA, a joint research institute of CU Boulder and NIST.

“Currently, there is no way to send quantum signals between distant superconducting processors like we send signals between two classical computers,” said Robert Delaney, the study’s lead author and former graduate student at JILA.

Delaney explained that the traditional bits that power a laptop are very limited: they can only take a value of zero or one, numbers that essentially account for most computer programming to date. In contrast, qubits can be zeros, ones, or through a property called “superposition” that exist as zeros and ones at the same time.

But working with qubits is a bit like trying to catch a snowflake in your warm hand. Even the smallest disturbances can cause this overlay to collapse, making it look like normal parts.

In the new study, Delaney and colleagues show that they can overcome this fragility. The team uses a thin piece of silicon and nitrogen to convert the signal from a superconducting qubit into a visible signal light– The same type of light that actually carries digital signals from one city to another over fiber-optic cables.

The researchers conducted experiments to extract it optical light of the qubit, but not disrupting the qubit in the process is challenging,” said study co-author Cindy Regal, JILA Fellow and Associate Professor of Physics at CU Boulder.

Quantum leap

She added that there are a lot of different ways to make a qubit.

Some scientists have synthesized qubits by trapping an atom in laser light. Others have experimented with including qubits in diamonds and other crystals. Companies like IBM and Google have begun designing quantum computer chips using qubits made of superconductors.

Superconductors are materials around which electrons can travel without resistance. Under the right conditions, superconductors will emit quantum signals in the form of tiny particles of light, or “photons” that oscillate at microwave frequencies.

This is where the problem begins, Delaney said.

To send these kinds of quantum signals over long distances, researchers will first need to convert microwave photons into visible light, or photons of light — which can emit sound in relative safety through fiber-cable networks across a city or even between cities. But when it comes to quantum computers, achieving this transformation is difficult, said study co-author Konrad Lehnert.

Partly because one of the main tools you need to convert microwave photons into photons of light is laser light, and lasers are an enemy of superconducting qubits. If a single photon of the laser beam hits your qubit, it will completely erase.

“The fragility of qubits and the fundamental mismatch between superconductors and laser light usually makes it difficult to read this kind of reading,” said Lennert, a fellow at the National Institute of Standards and Technology (NIST) and Gila.

secret codes

To get around this hurdle, the team turned to a medium: a thin piece of material called a photovoltaic transducer.

Delaney explained that the team begins by striking that chip, which is too small to be seen without a microscope, with laser light. When qubits’ microwave photons hit the device, they vibrate and emit more photons—but those photons now vibrate at an entirely different frequency. Microwave light goes in and visible light goes out

In the latest study, the researchers tested their transducer using a real superconducting qubit. They discovered that the thinner material could achieve this transducer while effectively keeping these deadly enemies, qubits and lasers, isolated from each other. In other words, none of the photons emitted by the laser light escaped again to disrupt the superconductor.

“Our PV converter does not have a significant impact on the qubit,” Delaney said.

The team hasn’t gotten to the point where it can transmit actual quantum information through its transducer. Among other problems, the device is not particularly effective so far. It takes about 500 microwave photonson average, to produce one song visible light Photon.

Researchers are currently working to improve this rate. Once they do that, new possibilities may emerge in the quantum world. Scientists could, in theory, use a similar set of tools to send quantum signals over cables that would automatically erase their information when someone tried to listen in.

In other words, Mission Impossible has become a reality, and it’s all thanks to sensitivity qubit.

Optical fibers can enhance the power of superconducting quantum computers

more information:
Robert Delaney, Superconducting qubit readings by means of a low-rebound photovoltaic conduction, temper nature (2022). DOI: 10.1038 / s41586-022-04720-2.

the quote: Physicists Made Leaps in Reading Qubits Using Laser Light (2022, June 15) Retrieved June 15, 2022 from

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