For the first time in history, the shot-noise limit has been broken, marking another breakthrough in the fields of quantum physics!
Shot noise or Poisson noise is a type of electronic noise that can be modeled using random mathematical objects consist of points randomly located in mathematical space. The process is commonly known as Poisson point process or simply Poisson process.
This phenomenon is typically observed in photon counting in optical devices, where shot noise is associated with the particle nature of light.
For instance, consider a photon stream (light) coming out of a laser pointer and hitting a board where a visible spot can be seen. In physics, the photons coming out of the pointer are emitted at random times. However, in the visible spot, billions of photons are traveling yet the fluctuations in the number of photons per unit of time varies infinitesimally.
If you were to turn down the brightness on the same laser only a few photons would hit the wall each second. The fluctuations in the number of protons at any given time become significant–this is known as shot noise.Another breakthrough in #QuantumPhysics has been achieved by researchers!Click To Tweet
Now, what is the shot-noise limit?
From the RP Photonics Encyclopedia: “A fundamental limit to the optical intensity noise as observed in many situations (e.g. in measurements with a photodiode or a CCD camera) is given by shot noise. This is a quantum noise effect, related to the discreteness of photons and electrons.”
Breaking the Shot-Noise Limit
For many years, theoretical physicists only predicted that taking measurements using photons in quantum states could potentially deliver an advantage over the typical measurements taken using light in non-quantum states.
This has been a theory that many experts believed to be impossible until a group of researchers from Griffith University in Australia set a new record in optical measurements using photons.
Apparently, the breakthrough could potentially help maximize the amount of information that could be extracted from individual particles of light in photonic quantum metrology.
In a statement given by Pryde to ScienceAlert, he said:
“When photons are entangled, their properties are correlated, or connected together. This means there is less randomness in the measurement. However, it turns out that these entangled states only work if the entangled photons are high-quality and don’t go ‘missing’.”
This limitation, known as the shot-noise limit, appears to happen because the randomness is creeping into optical measurements when each particle of light is accidentally absorbed or scattered in the measurement device, or in some cases, just simply not detected.
In the past, shot-noise limit has prevented researchers from achieving “the theoretical limits of super-sensitive measurements with photons in quantum states.” But, thanks to Pryde and his team, this is probably not the case anymore.
“What is new here is that we are able to make and measure high-quality photons with high efficiency (they don’t go missing),” Pryde went on to say. “And so we can show that the technique really works as described in the theory.”
The group of scientists passed a laser through a nonlinear crystal to break the shot-noise limit, ensuring that each property was carefully tailored to produce high-quality photons. After which, the photons were passed through a sample; the object being measured which according to the study was quartz crystal.
Pryde and his team were able to show that the shot-noise limit could be broken unconditionally using high-efficiency detectors to measure the photons. This further proved that random noise could be avoided when performing significantly precise optical measurements.
“It shows that photons in certain quantum states really can be used to make certain kinds of measurement better than when we don’t use quantum physics,” Pryde said. “We hope that future extensions can be used for precision measurement of sensitive samples.”
The researchers believe that it’s still early to speculate what those samples are. However, they agree that the method could potentially aid scientists in measuring any material using a small amount of light in the future.
Currently, what the scientists achieved has only proven that optical measurement is possible using photons in quantum states.