attoclock electron tunneling time

Attoclock Technique Breaks Ground in Measuring Electron Tunneling Time

Quantum Tunneling and the Ultrafast Challenge

Under the influence of an intense laser field, electrons may traverse the quantum tunneling barrier—an energy threshold normally insurmountable. This remarkable phenomenon, central to quantum mechanics and termed quantum tunneling, has attracted sustained academic interest.

Difficulties in Measuring Tunneling Duration

Accurately determining the duration an electron remains within a quantum tunneling barrier during strong-field ionization has long posed difficulties. Recently, physicists have devised sophisticated experimental instruments—attoclocks—capable of capturing ultrafast electron dynamics, potentially resolving this enduring scientific puzzle.

The Carrier-Envelope Phase-Based Attoclock Breakthrough

Although attoclocks hold promise for measuring electron tunneling times, most existing versions have fallen short, lacking in precision and conclusiveness. In a recent Physical Review Letters publication, scientists from Wayne State University and Sorbonne University introduced a new CEP-based attoclock technique, which utilises the carrier-envelope phase—an offset between a laser pulse's envelope and its oscillating field—to obtain more accurate tunneling time data.

Tunneling Time: An Unresolved Quantum Puzzle

"Tunneling time remains one of the enduring puzzles of quantum theory," said Wen, Li, the study's lead author, speaking to publisher website. "Attoclocks provide remarkably fine time resolution—down to mere attoseconds—making them a seemingly ideal tool. Yet, after twenty years of determined investigation, the question continues to elude a definitive answer."

How the New Attoclock Technique Improves Precision

The principal aim of Li and his team's recent investigation was to devise an advanced attoclock capable of measuring electron tunneling time with heightened precision. Unlike conventional attoclocks that infer temporal delays using elliptically polarized light—where the electric field traces an elliptical path—their method offers a novel approach.

Limitations of Conventional Attoclocks

While conventional attoclocks hold promise, they often demand complex modeling and hence produce results of limited reliability.

The Role of Circularly Polarized Light and CEP

In contrast, the approach proposed by Li and his team links elliptical readings to those obtained from circularly polarized light—where electric fields rotate in a circular motion—by capitalizing on the carrier-envelope phase.

Reducing Measurement Distortions

"Unlike traditional attoclock methods, the phase-resolved attoclock accurately follows the peak of the electric field—the precise instant at which electrons escape via tunneling," explained Li. "This approach minimizes non-temporal distortions that typically compromise the accuracy of the measurements."

Experimental Success and New Discoveries

The team has already trialed their novel phase-resolved attoclock through a series of experiments, yielding valuable new insights. Their findings indicate that electron tunneling time is minimal and that deflection angles are largely governed by ionization potential, with tunneling delays playing a fra smaller role.

Future Implications for Quantum Physics and Spectroscopy

The attoclock innovation introduced by Li and his team may soon pave the way for fresh insights into ultrafast quantum phenomena.

Virtually Zero Tunneling Duration

Li states, "Through our novel technique and combined theoretical insights, we reveal that the tunneling duration is virtually non-existent, with deflection angles clearly tied to ionization energies."

The Road to Zeptoclocks and Real-Time Chemistry Tools

"We are currently investigating the near-zero delays observed in the study. Given their minute scale, a 'zeptoclock' may be required. Moreover, owing to the robustness of the technique, we are developing it into a spectroscopic tool for real-time chemical analysis."

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