*ITAMP Lunch Seminar*
*Speaker:* Zlatko Minev (Yale University)
*Date:* Thursday, May 17th
*Time:* 12:00-1:00 pm
Includes Pizza.
*Title: *Catching and Reversing a Quantum Jump Mid-Flight
*Abstract: *A quantum system driven by a weak deterministic force while
under strong continuous energy measurement exhibits quantum jumps between
its energy levels. This celebrated phenomenon is emblematic of the special
nature of randomness in quantum physics. The times at which the jumps occur
are reputed to be fundamentally unpredictable. However, certain classical
phenomena, like tsunamis, while unpredictable in the long term, may possess
a degree of predictability in the short term, and in some cases it may be
possible to prevent a disaster by detecting an advance warning signal. Can
there be, despite the indeterminism of quantum physics, a possibility to
know if a quantum jump is about to occur or not? We answer this question
affirmatively by experimentally demonstrating that the completed jump from
the ground to an excited state of a superconducting artificial atom can be
tracked, as it follows its predictable ``flight,'' by monitoring the
population of an auxiliary level coupled to the ground state. Furthermore,
we show that the completed jump is continuous, deterministic, and coherent.
Exploiting this coherence, we catch and reverse a quantum jump mid-flight,
thus preventing its completion. This real-time intervention is based on a
particular lull period in the population of the auxiliary level, which
serves as our advance warning signal. Our results, which agree with
theoretical predictions essentially without adjustable parameters, support
the modern quantum trajectory theory and provide new ground for the
exploration of real-time intervention techniques in the control of quantum
systems, such as early detection of error syndromes.
*Location: *B-106 @ Center for Astrophysics (60 Garden Street)
*Directions: *After entering the lobby of the CfA, turn right to enter the
hallway of the B building. In the hallway, turn right again, B-106 will be
at the end of the hallway on the left side.
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