A New Method of Optical Distance Measurement

A new method of distance measurement using quantum physics to overcome the resolution limit. (Source: B. Mazhiqi, U. Paderborn)

Researchers at Paderborn University have developed a new method of distance measure­ment for systems such as GPS, which achieves more precise results than ever before. Using quantum physics, the team led by Leibniz Prize winner Christine Silberhorn has success­fully overcome the reso­lution limit, which causes the noise we may see in photos, for example.

Physicist Benjamin Brecht explains the problem of the reso­lution limit: “In laser distance measure­ments a detector registers two light pulses of different inten­sities with a time difference. The more precise the time measurement is, the more accu­rately the distance can be determined. Providing the time sepa­ration between the pulses is greater than the length of the pulses, this works well.” Problems arise, however, as Brecht explains, if the pulses overlap: “Then you can no longer measure the time dif­ference using conven­tional methods. This is known as the resolution limit and is a well-known effect in photos. Very small structures or textures can no longer be resolved. That’s the same problem – just with position rather than time.”

A further challenge, according to Brecht, is to determine the different inten­sities of two light pulses, simultaneously with their time difference and the arrival time. But this is exactly what the researchers have managed to do – “with quantum-limited preci­sion”, adds Brecht. Working with partners from the Czech Republic and Spain, the Paderborn physicists were even able to measure these values when the pulses overlapped by 90 per cent. Brecht says: “This is far beyond the resolution limit. The preci­sion of the measurement is 10,000 times better. Using methods from quantum information theory, we can find new forms of measurement which overcome the limi­tations of established methods.”

These findings could allow signi­ficant improve­ments in the future to the precision of appli­cations such as LIDAR, a method of optical distance and speed measure­ment, and GPS. It will take some time, however, before this is ready for the market, points out Brecht. (Source: U. Paderborn)

Reference: V. Ansari et al.: Achieving the Ultimate Quantum Timing Resolution, PRX Quantum 2, 010301 (2021); DOI: 10.1103/PRXQuantum.2.010301

Link: Integrated Quantum Optics, University of Paderborn, Paderborn, Germany

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