Dynamical coherence measures

Gregor Weihs

Seth J. Meiselman, Offir Cohen, M. F. DeCamp +1 more

We demonstrate the measurement of vibrational state coherence dynamics in liquid methanol using transient coherent spontaneous Raman scattering. The resulting lifetimes and quantum beat frequency agree with frequency-domain and coherent anti-Stokes Raman scattering measurements.

Ho-Joon Kim, Soojoon Lee

Quantum dynamics governs the transformation of static quantum resources, such as coherence and entanglement, in both quantum states and measurements. Prior studies have established that a quantum channel's state-cohering power can be converted into the state-entangling power without additional coherence. Here, we complete this coherence-to-entanglement paradigm by demonstrating that a channel's measurement-cohering power can likewise be converted into the measurement-entangling power. This result reinforces, on the dynamical level, the intuition that entanglement emerges as a manifestation of coherence. To formalize this picture, we develop resource theories for measurement-cohering and measurement-entangling powers and characterize the structure of incoherent measurements to analyze measurement-coherence generation. Furthermore, we show that the state-cohering power of a quantum channel is equivalent to the measurement-cohering power of its adjoint map, and a corresponding equivalence also exists between the state-entangling power and the measurement-entangling power.

Jan Peřina

C. L. Liu, Da-Jian Zhang, Xiao-Dong Yu +2 more

Seth Lloyd, Lorenza Viola

The ability to perform measurements on a quantum system, combined with the ability to feed back the measurement results via coherent control, allows one to control the system to follow any desired coherent or incoherent quantum dynamics. Such universal dynamical control can be achieved, in principle, through the repeated application of only two coherent control operations and a simple ``Yes-No'' measurement. As a consequence, a quantum computer can simulate an arbitrary open-system dynamics using just one qubit more than required to simulate closed-system dynamics.