UAM scientists suggest that the most exotic and complex quantum phenomena occur where the emission is weakest

Oct. 8 () –

Scientists from the Autonomous University of Madrid (UAM) argue that The most exotic and complex quantum phenomena occur at frequencies where quantum systems emit the least light.

In a recent article invited by ‘The Royal Society’, published in the prestigious magazine ‘Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences’a team from the Autonomous University of Madrid (UAM) proposes to explore the deepest quantum phenomena. To do this, they suggest scanning at frequencies where quantum systems emit less light.

Traditionally, the characterization of these systems -such as atoms, molecules or quantum dots- It is based on the measurement of light at its spectral peaks, that is, at the frequencies where they emit the most..

However, the researchers suggest that the most complex and exotic quantum interactions paradoxically occur where the emission is weakest.

Specifically, the team proposes to study the multi-photon spectrum, known as the N-photon spectrum, to reveal processes that are not visible in conventional single-photon measurements. According to the researchers, these processes include phenomena such as: virtual transitions, where electrons decay to lower energy levels, skipping several intermediates; entanglement, when two or more photons are linked regardless of distance; squeezing, a property that takes Heisenberg’s uncertainty principle to its limit; and quantum interference, which affects the emission of a certain number of photons.

“In these situations, the correlations are quantum in nature and very strong, so they could be exploited for quantum applications and technologies that the future holds for us.”“add the authors.

Elena del Valle, professor at the UAM, and Fabrice Laussy, researcher at ICMM-CSIC, have been researching this type of processes for more than a decade. Together with Eduardo Zubizarreta Casalengua, who completed his thesis with them at the UAM and is now a postdoctoral fellow, they collaborate with Kai Müller’s experimental group at the Technical University of Munich, working on the experimental demonstration of these ideas.

This work has been highlighted by The Royal Society within the framework of the 15th anniversary of the Newton International Fellowship, which del Valle obtained in 2009. “These discoveries bring us closer to a future where these properties can be exploited technologically,” the authors point out.

“Our research is based on two theoretical pillars: a theory of frequency-resolved photon correlations and the interaction between classical and quantum fields.“, they explain.

The researchers note that frequency-resolved multiphoton correlations “offer a unique window into the quantum dynamics of, for example, qubits (two-level systems), and their emission, resonance fluorescence.”

“As Newton once expressed: ‘I seem to have been but a child playing on the seashore, while the great ocean of truth lay unexplored before me.'”the authors conclude.