Optical Single-Electron Detector

Leiden physicists have now identified a molecule that is sensitive enough to detect an electron at a distance of hundreds of nanometers. (Source: U. Leiden)

Physicists have been able to mani­pulate single electrons for some time. But they can only see them as part of an electric current, consisting of thousands of electrons. Now imagine if we could detect an electron opti­cally using one single molecule. Then you could indi­rectly see indi­vidual electrons that are actually on their own. Perhaps in the future, a quantum computer could use this method to locate its qubits with light, so it won’t disturb their ambiguous spin quantum state – an essential requirement for quantum computers. Leiden physicist Michel Orrit and his group have now taken a first step towards deve­loping this technique, by identifying a molecular system that is sensi­tive enough to detect an electron from as far as hundreds of nanometers away.

The researchers, including Zoran Ristanović and Amin Moradi, found that the fluorescent molecule dibenzo­terrylene (DBT) possesses two vital properties for single charge detection – provided that it is included in a molecular crystal of 2,3-dibromo­naphthalene. First of all, DBT molecules fluoresce, emitting a narrow spectrum of visible light that is stable over longer periods of time. Secondly, those narrow spectral lines shift signi­ficantly in the presence of an electric field. This will become the telltale sign of a nearby charge, because charges generate such an electric field.

Orrit and his col­leagues show that they can easily detect electric fields in the order of 1 kV/cm with a DBT-molecule. This is more than enough sensi­tivity for detecting a single electron at 100 nm away, whose electric field there is about 1.5 kV/cm. Using multiple mole­cules responding similarly to an electric field, the physicists could even use triangu­lation to find the electron’s location, similar to GPS. The next step is detecting an actual electron. The research team is currently building a single-electron device for that experi­ment. (Source: U. Leiden)

Reference: A. Moradi et al.: Matrix-induced Linear Stark Effect of Single Dibenzoterrylene Molecules in 2,3-Dibromonaphthalene Crystal, ChemPhysChem 20, 55 (2019); DOI: 10.1002/cphc.201800937

Link: Quantum Optics Group, Huygens-Kamerlingh Onnes Laboratory, LION, Leiden, The Netherlands

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