TU Wien shows how reshaping photons could lift qubit transfer from 54% to 100%

[Doomsday15]

One of the quiet problems in quantum networking is simply catching a photon. SciTechDaily reports on work from TU Wien, published in Physical Review Letters, which proposes a way to raise the success rate of passing quantum information between two qubits from about 54 percent to a theoretical 100 percent

When one qubit emits a photon to send its state to another, the receiving qubit often fails to absorb it. With conventional setups the absorption success rate tops out at around 54 percent, so nearly half of the photons, and the information they carry, are lost along the way

The problem is the shape of the pulse. An emitted photon naturally rises sharply and then fades away, but a qubit absorbs best when the pulse arrives as the mirror image of that, building up slowly and ending sharply. The team, Zeyu Kuang, Oliver Diekmann, Stefan Rotter and Carlos Gonzalez-Ballestero, propose placing both qubits in a waveguide whose dispersion is carefully engineered, so the different frequency components of the pulse travel at different speeds and the waveform flips on its way

The key word is passive. There is no need for fast active control or modulators during transmission, because the waveguide itself does the reshaping, using the time reversal symmetry of quantum mechanics. Gonzalez-Ballestero said the results indicate the required setup should be technically feasible

This is theoretical work based on modelling and simulation, so nobody has built the device yet. Still, losing half of every transfer is a huge handicap for quantum networks, cryptography and modular quantum computers. A passive fix that could work with existing chip fabrication would be a valuable step if experiments confirm it

Could passive waveguides solve photon loss in quantum networks? And how soon could this be tested in a lab?

From 54 To 100 Scientists Reveal A Potential Breakthrough In Quantum Technologyscitechdaily.com