Quantum Noise and Backaction in Semi- and Superconducting Nanostructures

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*****NON-TECHNICAL ABSTRACT*****Quantum mechanics demands that the act of measuring the position of a particle such as an electron will influence the particle by changing its velocity. The famous statement that such a measurement acts back on the object being measured is known as Heisenberg's Uncertainly Principle. One often speaks of a measurement as having some "backaction" on the object being measured. This single-investigator award supports research that will directly investigate these fundamental issues. Recent technological advances in the PI's laboratory have led to ultrasensitive charge detectors for which the noisy forces that cause to backaction can be directly observed. These detectors will be used to observe the position of a single electron confined to a nanometer-sized region in semiconductor known as a quantum dot. The backaction forces that influence the electron position will independently be monitored. Measurements like these will allow a direct investigation of the physical processes underlying the Uncertainty Principle. Results from this research will also have implications for measurement of bits in quantum computers, which are expected to be able to solve problems classical computers cannot. Students involved in this project will receive training in a broad array of advanced fabrication and measurement techniques, leaving them well-prepared for a career in academia, industry or government.*****TECHNICAL ABSTRACT*****There is a deep relationship between Heisenberg's Uncertainty Principle and noise in a quantum system. Since a detector necessarily influences a system it is measuring, the quantum mechanical noise produced by a system should be directly influenced by the noisy force (the backaction) exerted on it by a detector. This single-investigator award supports research that will directly investigate these fundamental issues. Recent technological advances in the PI's laboratory have led to ultrasensitive charge detectors for which the intrinsic noise that leads to backaction can be observed. By using these detectors to monitor the position of a single electron in a semiconductor device, this research will take a direct look at the physical processes underlying the Uncertainty Principle. Results from this work will also have implications for the field of quantum computation, in which a central problem is the measurement of the state of a quantum bit. Students involved in this project will receive training in a broad array of advanced fabrication and measurement techniques, leaving them well-prepared for a career in academia, industry or government.