Laser-Driven Plasmas Unlock Attosecond Bursts of Quantum Light

A new pathway for exploring relativistic nonlinear quantum electrodynamics without external particle beams has been identified by Vedin Dewan of Princeton University in collaboration with Texas A&M University and colleagues. Intense, ultrashort laser pulses generate relativistic electron bunches within plasmas, resulting in attosecond bursts of two-photon emission and a new source of correlated photon pairs. The work offers a physically justifiable method for analysing nonlinear QED phenomena in complex laser-plasma interactions, quantifying the emission rate through parameters including the fine-structure constant and relativistic curvature frequency, and providing guidance on isolating quantum effects from classical ones.

Laser-driven plasmas enhance correlated photon emission and access nonlinear quantum electrodynamics

Correlated photon pair emission rates have improved by a factor of approximately 2.5 × 10−4 per pulse at higher energies, a substantial increase over previous methods. Earlier techniques necessitated dedicated, high-energy particle sources; this new approach generates the requisite relativistic electrons directly within laser-driven plasmas, simplifying experimental setups and reducing costs. A maximum Lorentz factor of 200 for these electrons was key, enabling access to the nonlinear quantum electrodynamics regime previously inaccessible without external beams.

Photon-pair emission is confined to the nanometer scale in space and the attosecond scale in time through ultrafast strong-field laser and plasma physics, offering a framework for relativistic nonlinear quantum electrodynamics. High-energy electrons generate during these laser-plasma interactions, rather than requiring an external particle beam. An intense ultrashort laser pulse accelerates dense electron bunches to relativistic energies, resulting in attosecond bursts of two-photon emission and an ultrabroadband source of correlated photon pairs.

The rate of two-photon emission is proportional to the product α 2 γω turn, where α is the fine-structure constant, γ is the Lorentz factor, and ω turn is the local relativistic curvature frequency. Photon pairs with stronger correlations, useful for photon entanglement, emit at a lower rate, estimated as α 2 γ 2 ω turn E ⊥ /E S, where E ⊥ is the laser electromagnetic field determining the transverse Lorentz force, and E S is the Schwinger critical field. Simulations demonstrate that electrons within laser-driven plasmas can reach a Lorentz factor of approximately 100 and 200, while the instantaneous angular turning frequency, governing emission characteristics, depends on electron velocity and the transverse Lorentz force. These simulations provide crucial insights into the dynamics of photon emission.

Relativistic electron bunch acceleration and attosecond photon emission from laser-plasma

Intense laser pulses focused onto plasma initiate the process by generating and accelerating dense electron bunches to relativistic energies, providing the source of particles needed to study quantum effects without external beams. These energies, where the Lorentz factor reached 200 in these experiments, allow scientists to probe the area of nonlinear quantum electrodynamics. The accelerated electrons then emit photons, confined to a nanometer scale in space and an attosecond timescale in time; an attosecond being equivalent to a billionth of a billionth of a second, representing an incredibly short duration.

Relativistic electrons generate within plasma by intense laser pulses, eliminating the need for external particle beams. Subsequently, these electrons, accelerated to energies giving Lorentz factors of approximately 100 to 200 in experiments, emit photon pairs confined to nanometer spatial and attosecond temporal scales. Photon pair emission rates are expressed as a product of α 2 γω turn, where α is the fine-structure constant, γ is the Lorentz factor, and ω turn is the local relativistic curvature frequency. Pairs with the strongest correlations emit at a lower rate, estimated as α 2 γ 2 ω turn E ⊥ /E S, where E ⊥ is the laser electromagnetic field and E S is the Schwinger critical field.

Laser-plasma acceleration and theoretical emission rate estimations for relativistic electron beams

Generating high-energy electrons is a pathway to explore nonlinear quantum electrodynamics, the bizarre area where light and matter interact at extreme intensities. Current methods for creating the necessary relativistic particle beams are complex and expensive, limiting access to these fundamental investigations. This approach offers a compelling alternative, producing these electrons directly within laser-driven plasmas; however, the abstract highlights a reliance on theoretical estimations of emission rates.

Despite acknowledging that these emission rate calculations currently rely on estimations, this remains important for charting a course towards experimental verification of nonlinear quantum electrodynamics. Precisely quantifying these rates is challenging, but establishing a theoretical framework, even with approximations, provides vital guidance for interpreting future experimental data from facilities like ELI-NP. This allows scientists to discern genuine quantum effects from classical background noise within complex laser-plasma interactions, accelerating progress in this field. The method generates correlated photon pairs within laser-driven plasmas, removing the need for bulky external particle beam infrastructure. Intense laser pulses directly produce relativistic electrons, particles travelling close to the speed of light, inside the plasma itself, initiating two-photon emission at a nanometer scale and attosecond timescale. Understanding the emission rate, linked to parameters like the Lorentz factor and relativistic curvature frequency, allows for isolating genuine quantum effects from classical behaviours within these complex interactions.

The research demonstrated that high-energy electrons can be generated within laser-driven plasmas, offering a new means of exploring relativistic nonlinear quantum electrodynamics without requiring external particle beams. This is significant because it simplifies the process of studying extreme light-matter interactions and potentially lowers the barriers to entry for researchers in this field. The study characterised the rate of two-photon emission from these relativistic electrons, linking it to factors such as the Lorentz factor and laser field strength. Researchers calculated emission rates using estimations, providing a theoretical foundation for future experimental verification of quantum effects within laser-plasma interactions.