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A clock normally needs a beginning. Set the starting point, count the ticks and calculate how much time has passed. A quantum system built from excited helium atoms could offer a different approach.
Researchers at Uppsala University have shown that complex interference patterns inside highly excited atoms can act as timestamps. Instead of counting regular oscillations from a known zero point, the method reads a distinctive quantum pattern and matches it to theory to determine how much time has elapsed.
The team calls the method a "quantum watch," rather than a clock. Its key signal comes from quasiunique beat signatures, or QUBS, produced when many Rydberg states interfere. In experiments, those patterns allowed the researchers to determine elapsed time with femtosecond-scale accuracy and expose a small drift in equipment normally used to set timing.
Ordinary mechanical, quartz and atomic clocks rely on repeated oscillations. Time is determined by counting those cycles from an established reference point. The Uppsala approach works differently because the quantum interference pattern itself changes as time passes.
"You can compare it to how you can look at a measuring tape and see how far you are from the start. Regardless if it is 5 centimeters or 4000 meters, we could show that it is possible to look at the probability that these Rydberg states can be ionised by another light pulse. And by studying only a short time interval, we could by comparing with theoretical models, directly read off how much time had passed since the Rydberg states were created," said Johan Söderström, who leads the research group in the Division of X-ray Photon Science at Uppsala University's Department of Physics and Astronomy.
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Researchers at Uppsala University have shown that complex interference patterns inside highly excited atoms can act as timestamps. Instead of counting regular oscillations from a known zero point, the method reads a distinctive quantum pattern and matches it to theory to determine how much time has elapsed.
The team calls the method a "quantum watch," rather than a clock. Its key signal comes from quasiunique beat signatures, or QUBS, produced when many Rydberg states interfere. In experiments, those patterns allowed the researchers to determine elapsed time with femtosecond-scale accuracy and expose a small drift in equipment normally used to set timing.
Ordinary mechanical, quartz and atomic clocks rely on repeated oscillations. Time is determined by counting those cycles from an established reference point. The Uppsala approach works differently because the quantum interference pattern itself changes as time passes.
"You can compare it to how you can look at a measuring tape and see how far you are from the start. Regardless if it is 5 centimeters or 4000 meters, we could show that it is possible to look at the probability that these Rydberg states can be ionised by another light pulse. And by studying only a short time interval, we could by comparing with theoretical models, directly read off how much time had passed since the Rydberg states were created," said Johan Söderström, who leads the research group in the Division of X-ray Photon Science at Uppsala University's Department of Physics and Astronomy.
Quantum interference offers a radically different way to measure time
A new “quantum watch” uses changing interference patterns inside excited helium atoms to determine how much time has passed without counting from a defined time zero. Uppsala University researchers fo...
