Dr. Keith C. Schwab
Cornell University
Probing Quantum Mechanics with Mechanical Structures
The fundamental theory which describes the behavior of the microscopic world of atoms, electrons, and photons is called quantum mechanics. Quantum mechanics has shown itself to be correct in laboratory experiments and tests, with no known exceptions. In spite of this, there are problems: quantum mechanics allows particles to exist in two places simultaneously (observations in laboratory experiments show this to be true.) If the small particles are allowed to behave in this strange way, and larger objects are made of these small particles, then why can not large objects be in two places simultaneously? This behavior is far outside our normal experience of reality. We are pursuing experiments to do just this, to produce ever larger objects in two spatial locations at the same time. We are using the most advance tools science gives us to do this: nanofabrication, ultra-low temperature physics, and quantum electronic devices. We will either succeed to show quantum mechanics is true at bizarrely large length scales, or we will fail and possibly find new features to quantum mechanics which are not yet known. Both possibilities would change our view of the physical world.
Standard quantum mechanics allows the possibility of superposition states of macroscopic objects, states that are totally outside our classical experience of reality. Some prominent physicists have speculated that these intrinsically quantum states may be blocked by an as-of-yet undiscovered fluctuating field which produces "spontaneous localization" for objects of large enough mass or length scales. Another proposed mechanism is a result of the interaction between quantum mechanics and gravitation. To address this, pushing the boundary of the quantum regime to larger length scales, we will probe the formation of quantum entanglement between a flexural mechanical structure with masses ~10-15Kg, and a quantum electronic device, a superconducting Cooper-Pair Box qubit. This experiment is now only very recently possible due to the latest advances in nano-electro-mechanical devices, superconducting qubit technology, and quantum non-demolition readout techniques. Beyond the formation of bizarre entangled and superposition states, we will be able for the first time to quantitatively explore of the decoherence rate of mechanical structures, and begin to search for deviations from standard quantum mechanics. Furthermore, we will microfabricate optomechanical devices for experiments preformed in the laboratory of A. Aspelmeyer and A. Zeilinger to demonstrate entanglement with quantum optical fields.
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