A new protocol thwarts the limitation of decoherence

Researchers have shown a new quantum detection technique that goes far beyond conventional methods, potentially accelerating progress in fields ranging from medical imaging to research in fundamental physics, as shown in a study published in Nature communications.

For decades, quantum sensors’ performance has been limited by decoherence, which is an unpredictable behavior caused by environmental noise.

“Decoherence increases from the state of a quantum system, erasing any quantum detection signal,” said Eli Levenson-Falk, principal of the study, associate professor of physics and astronomy at the USC Dornsife College of Letters, Arts and Sciences and Associate Professor of Electricity and IT of the USC Viterbi Engineering School.

Quantum detection is the use of quantum systems (such as atoms, light particles or qubits) as sensors to measure physical quantities (such as brain activity, ultra-preccosed clocks or gravity anomalies) with extreme precision, often exceeding the limits of conventional sensors. Detection devices use quantum properties (such as overlapping, tangle and consistency) to detect tiny signals that would otherwise be drowned by noise.

“Consider it as trying to hear a weak whisper in a noisy space,” said Malida Hecht, a doctoral student in physics at USC Dornsife and the main study of the study. “Quantum detection devices detect too small or weak things for normal measurement tools to notice.”

Thwart the decoherence with a new stabilized coherence protocol

In the new study, the research team has temporarily thwarted the problem of long -standing decoherence using a new stabilized protocol of predetermined coherence on the qubit of their experience, stabilizing a key property of the quantum state.

The study protocol was based on the theory derived by co-authors Daniel Lidar (professor of Viterbi of engineering and professor of chemistry and physics and astronomy at the USC) and Kumar Saurav (doctoral student in electrical engineering at USC Viterbi).

This experience has considerably improved the measurement of small frequency changes in quantum systems. Levenson-Falk said that the Stabilized Study Stabilized Detection Protocol allows the detection signal, which takes the form of a change in the quantum state, to grow larger than it would do with the detection measure of the standard protocol.

This stabilization could be crucial for applications where the detection of subtle signals is essential. “The larger signal is easier to detect, giving improved sensitivity,” said Levenson-Falk.

“Our study gives the best sensitivity to detect the frequency of a qubit to date. More importantly, our protocol requires no feedback and no additional control or measurement resources, which makes it immediately applicable in various quantum and quantum sensors technologies.”

165% improvement in detection capacity

The researchers have demonstrated their protocol on a superconductive qubit, reaching up to 1.65 times better efficiency per measure compared to the standard protocol known as Ramsey interferometry. Theoretical analysis has indicated potential improvements that are up to 1.96 times in certain systems.

Levenson-Falk said that his experimental detection demonstration with a stabilized state shows that there are means of improving quantum sensors without resorting to complex techniques such as real-time feedback or sensors.

“It also shows that we have not yet extracted all the possible information from these types of measures. Even better detection protocols are there, and we could use them to have immediate impacts in the real world.”