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Fastest Timer
Chalcogenide:
There many time measurements units that are mostly used for Time Correlated Single Photon Counting (TCSPC) applications, but in general they work with any pair of digital signals that provide a start and a stop to said unit.
An (incomplete) list of manufacturers is for example Becker & Hickl, PicoQuant, Swabian Instruments. They usually get down to resolutions of 1 ps or less, with timing jitter quite easily below 10 ps rms. They are not cheap, obviously.
It is not that difficult to get down to 100 ps or so time resolution by using an FPGA and exploiting either their IODELAY resources or a bunch of carry chains, but I am not a VHDL wizard so I don't really know the details.
You can also use a beefy oscilloscope...
RoGeorge:
--- Quote from: raptor1956 on June 17, 2021, 06:51:10 am ---What LIGO does using interferometry isn't exactly like timing as it's more of a differential (relative) thing than an absolute thing.
--- End quote ---
I would like to point out that _any_ measurement is a differential thing and _not_ absolute. By definition, to measure something means "to compare it with the etalon unit", so it is always relativ to the etalon. Even a wristwatch, or a classic timer as a start/stop counter is still differential (relative) to its internal timebase.
- Another possible method to measure a very short pulse would be a Streak Camera, best time resolution 180 femtoseconds according to https://en.wikipedia.org/wiki/Streak_camera
- Another method might be to measure the very short pulses as a frequency comb to deduce the pulse width. There were some recent Nobel Prize awarded in the short pulses and frequency combs area of optics (these were used to measure time in the range of attoseconds or so, some techniques might overlap with the ones used in streak camera, IDK)
https://www.nobelprize.org/prizes/chemistry/1999/press-release/
https://www.nobelprize.org/prizes/physics/2005/summary/
If the OP question was about commercial start/stop counters/timers usually found in an EE lab, then I don't know which ones are the fastest. Also no idea how they measure sort pulses at NIST, but I suspect the shortest pulses might require a more elaborated setup than a COTS timer/counter.
Time related tech, NIST level:
Also from BIPM, but more general:
What exactly has to be measured matters a lot when pushing the limits of technology, so without a goal and a measuring setup example is hard to tell what would be the top available performance.
What has to be measured with that timer? Was the OP question about a specific experiment to measure, or about the best available timer to buy for an EE lab?
David Hess:
--- Quote from: raptor1956 on June 16, 2021, 12:59:50 am ---For example, if I wanted to measure the speed of light more directly by sending a beam to a mirror some distance away then bouncing it back the round trip time if the mirror was 100m away would be about 667ns, but to provide 3 digits precision you need a timing system capable of about 1e-10 seconds. To get 6 digits you'd need a timer with a resolution of about 1e-13 seconds. So, what is the fastest timers around?
--- End quote ---
Do you mean fastest or highest resolution? Usually those sorts of measurements are made with multiple samples in which case averaging can achieve incredible resolutions. Even my worst timer/counter with averaging can achieve 0.1 picosecond or 1e-13 resolution, and my best is better than 0.001 picoseconds or 1e-15 with 9 digits.
Single shot timing measurements are easily feasible to 10 picoseconds, and 1 picosecond resolution is not much more difficult using analog techniques.
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