One of the most complex problems that scientists face when working with quantum information is to ensure that the qubits remain secure. This is because every time they rewrite, measure, or delete even one qubit, neighboring qubits can be damaged, leading to a lack of information.
A new study from the University of Waterloo researchers suggests a solution to this problem. The study’s authors have devised a way to control laser light using qubits.
They even made an experiment to make this task almost impossible. The experiment involves checking and resetting the trapped ion qubit to a known state without any damage or disturbance to neighboring qubits that are only a few micrometers apart.
“This discovery could influence future research in the field, including improving quantum generators, improving speed and capabilities for tasks like quantum simulations in machines that already exist today, and implementing error correction.” said readers.
Why do we usually use qubits to store?
Current methods for storing qubits have several limitations. For example, they often require additional resources such as correction qubits or passive mechanisms to correct errors.
This can lead to a loss of coherent time, the time the qubits remain in an unperturbed quantum state. Such methods can also introduce new errors during the design process, reducing overall efficiency and reliability.
These limitations make it very challenging to manipulate or even obtain qubits. The students came up with an interesting solution to this problem. They work on two different technologies; ion trap qubits and beam holographic structure.
The first work was done to read, reset, and control qubits using laser light. During this process, qubits represent ions that are trapped in an electromagnetic field. The latter is used in manipulating laser light through optical objects such as holograms.
They decided to use the two technologies together to control the laser light so that it does not damage any of the qubits in the system while working on a single qubit.
Tricks to defeat qubits without destroying them
The authors of the study decided to change the quantum state of the qubit. So, first, they calculated its quantum state using center-of-circle measurements, a technique in quantum computing where the state of a qubit is measured while other operations are still in progress.
They used a precisely controlled laser and qubit structure of traps, using holographic imaging technology. This combined process keeps the light focused on its target and prevents it from reaching other qubits.
However, “the target ion scatters photons in all directions during this process. Even with perfect control over the light, there is still a risk that the scattered photons can damage the quantum state of nearby qubits, which limits how we can protect them,” Rajibul Islam, author of the study and professor at the University of Waterloo. said.
The holographic technique allowed the researchers to control and block the scattered photons. As a result, the experiment was successful and did not cause any disturbance or damage the neighboring qubits.
“We show that it is possible to reset the state and state-measurement of a trapped ion, achieving >99.9% fidelity in preserving the ion-qubit ‘pocket’ while the qubit ‘order’ is being reset, and >99.6% integrity when applying the detection light for 11 μs to a neighbor at a distance of 6 μm,” the study authors said.
This is a great achievement because until now, it was considered almost impossible to measure a single qubit without shaking everything around it. “Every expert in our field says it’s a bad idea not to try because it’s so weak,” Islam added.
However, we proved, “It is possible to destroy any qubit you want while keeping the quantum information in other qubits you don’t want to destroy,” said Sainath Motlakunta, the first author of the study and a postdoctoral fellow in the department. University of Waterloo said.
Studies are published in journals Natural communication.
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