Scientists Use Laser To Cool Small Area Of Film To Absolute Zero For Highly Sensitive Sensors

Recently, researchers at the University of Basel announced the successful development of a new method that can cool small areas of film to temperatures very close to absolute zero (minus 273.15 degrees Celsius) using only a laser. This highly cooled film, according to the report, may be used in the future for extremely sensitive sensors.
German astronomer Johannes Kepler came up with the idea of a solar sail 400 years ago, which is a spacecraft that uses the light pressure of sunlight for cosmic navigation and can be used to allow ships to navigate through space. He believed that when light is reflected by an object, a force is exerted. He also used this theory to explain why the tails of comets point away from the sun.
The team was led by Dr. Philipp Treutlein and Dr. Patrick Potts. Their findings were just recently published in the scientific journal Physical Review X.
No measurement feedback
Today, atoms and other particles are slowed and cooled using the power of light. A sophisticated instrument is usually required for this purpose. What is special about the above-mentioned team's approach is that they achieve this cooling effect without making any measurements.
According to the laws of quantum mechanics, feedback loops often require measurement processes that can lead to changes in quantum states and thus cause disturbances. To prevent this, the researchers at the University of Basel created a system called a "coherent feedback loop" in which the laser acts as both a sensor and a damper.
They achieved this by suppressing and cooling the thermal vibrations of a silicon nitrate film about half a millimeter in size. In their experiments, the researchers aimed the laser beam at the film and fed the light reflected from the film into a fiber optic cable. During this operation, the membrane's vibration produced small changes in the oscillation phase of the reflected light.
The information about the immediate state of motion of the membrane contained in the oscillation phase was then used, with a time delay, to apply the right amount of force to the membrane at the right moment using the same laser. The researchers used a 30-meter long fiber optic cable to achieve an optimal delay of about 100 nanoseconds.
Approaching absolute zero
The postdoctoral researcher and his colleagues at the University of Basel in Switzerland cooled the membrane to 480 microKelvin, or less than one thousandth of a degree above absolute zero.
In the next stage they will refine the experiment to bring the membrane to its oscillating quantum mechanical ground state - the lowest temperature attainable. The creation of the so-called squeezed states of the membrane should be conceivable.
Such states are of particular interest for sensor structures due to their ability to improve measurement accuracy. In the future, atomic force microscopy for scanning surfaces at nanometer resolution will be a potential application for such sensors.