[ad_1]
A team from Dartmouth College and MIT designed and implemented the first laboratory test to successfully detect and characterize a class of "non-Gaussian" complex noise processes commonly encountered in superconducting systems quantum computing systems.
The characterization of non-Gaussian noise in superconducting quantum bits is a crucial step in making these systems more accurate.
The joint study, published today (16 September 2019) in Nature Communications, could help accelerate the realization of quantum computing systems. The experiment was based on previous theoretical research conducted in Dartmouth and published in Letters of physical examination in 2016.
"This is the first concrete step toward attempting to characterize more complex types of noise processes than is generally assumed in the quantum domain," said Lorenza Viola, a physics professor at Dartmouth, who led the study. 2016 as well as the theoretical component of the present. job. "As qubit consistency properties are constantly improved, it is important to detect non-Gaussian noise in order to build the most accurate quantum systems possible."
Quantum computers are distinguished from traditional computers by going beyond the "on-off" binary sequencing favored by classical physics. Quantum computers rely on quantum bits, also called qubits, built from atomic and subatomic particles.
Essentially, qubits can be placed in a combination of "active" and "off" positions at the same time. They can also be "entangled", which means that the properties of one qubit can influence another at a distance.
The superconducting qubit systems are considered one of the main competitors in the race for the construction of evolutionary and efficient quantum computers. But, like other qubit platforms, they are very sensitive to their environment and can be affected by both external noise and internal noise.
External noise in quantum computing systems could come from control electronics or parasitic magnetic fields. Internal noise could come from other uncontrolled quantum systems such as material impurities. The ability to reduce noise is a major objective of the development of quantum computers.
"The problem of noise is the biggest barrier to having quantum computers on a large scale," said Leigh Norris, Dartmouth postdoctoral fellow and co-author of the study. "This research pushes us toward understanding noise, which is a step toward cancellation and the hope of having a reliable quantum computer someday."
Unwanted noise is often described in terms of simple "Gaussian" models, in which the probability distribution of random noise fluctuations creates a familiar bell-shaped Gaussian curve. Non-Gaussian noise is harder to describe and detect because it does not fall within the validity of these assumptions and may simply be less so.
Whenever the statistical properties of the noise are Gaussian, a small amount of information can be used to characterize the noise – i.e., correlations at only two distinct moments, or equivalently, in terms of frequency domain description. noise". spectrum."
Because of their high sensitivity to the environment, qubits can be used as sensors for their own noise. Building on this idea, researchers have made progress in developing techniques for identifying and reducing Gaussian noise in quantum systems, similar to the operation of noise-canceling headphones.
Although less common than Gaussian noise, the identification and removal of non-Gaussian noise is an equally important challenge for the optimal design of quantum systems.
Non-Gaussian noise is distinguished by more complex correlation models that involve several moments in time. As a result, it is necessary to have a lot more noise information to be able to identify it.
In this study, researchers were able to estimate the characteristics of non-Gaussian noise by using information on correlations at three different moments, corresponding to what is known as the "bispectrum" in the frequency domain.
"This is the first time that a detailed, frequency-resolved non-Gaussian noise characterization can be performed in a lab with qubits. This result greatly expands the toolbox we have available to perform accurate noise characterization and thereby create better and more stable qubits in quantum computers, "said Viola.
A quantum computer that can not detect non-Gaussian noise could easily be confused between the quantum signal it is supposed to process and the unwanted noise in the system. The protocols for obtaining non-Gaussian noise spectroscopy did not exist prior to the 2016 Dartmouth study.
Although the MIT experiment to validate the protocol does not immediately make large-scale quantum computers virtually viable, it is an important step in making them more accurate.
"This research started on the whiteboard. We did not know if anyone would be able to put it into practice, but despite significant conceptual and experimental challenges, the MIT team did, "said Felix Beaudoin, formerly post- Ph.D. student from the Viola group's Dartmouth group, who also played a key role. role of bridge between theory and experience in the study.
"It was an absolute joy to collaborate with Lorenza Viola and her fantastic theory team at Dartmouth," said William Oliver, professor of physics at MIT. "We have been working together for several years on several projects and, while quantum computing is moving from scientific curiosity to technical reality, I foresee the need to strengthen this interdisciplinary and interinstitutional collaboration."
According to the research team, additional years of work are still needed to perfect the detection and suppression of noise in quantum systems. In particular, future research will move from a single-sensor system to a two-sensor system to characterize noise correlations between different qubits.
References:
"Non-Gaussian Noise Spectroscopy with a Superconducting Sensor" by Youngkyu Sung, Felix Beaudoin, Leigh M. Norris, Fei Yan, David Kim K., Jack Y. Qiu, Uwe von Lupke, Jonilyn L. Yoder, Terry P. Orlando, Simon Gustavsson, Lorenza Alto and William D. Oliver, September 16, 2019, Nature Communications.
DOI: 10.1038 / s41467-019-11699-4
"Spectroscopy of Qubit noise in non-Gaussian phase-shifted environments" by Leigh M. Norris, Gerardo A. Paz-Silva and Lorenza Viola, April 14, 2016, Letters of physical examination.
DOI: 10.1103 / PhysRevLett.116.150503
[ad_2]
Source link