RSS icon
Twitter icon
Facebook icon
Vimeo icon
YouTube icon

Schrodinger's Cat -- The Movie

April 19, 2010 - 12:30pm
Speaker: 
John Martinis
Institution: 
UC Santa Barbara

The thought experiment of Schrodinger's cat illustrates the wave-particle duality in quantum mechanics, which originates from the two distinct ways in which a quantum state may change: a linear (unitary) evolution according to the Schrodinger wave equation, and a nonlinear (projective or collapse) evolution due to measurement. A model system to observe this collapse is the harmonic oscillator, since a “Schrodinger's cat state” can be prepared as a superposition of coherent states, and its subsequent evolution becomes probabilistic due to system decoherence. Here we present a movie of the collapse of the cat state from a coherent to incoherent superposition, obtained by measuring the cat state during its decay for 60 time steps. Movies can be downloaded atwww.physics.ucsb.edu/~martinisgroup.

The cat states are prepared by coupling a superconducting phase qubit to a high-Q coplanar wave guide resonator. The qubit is used to pump photons into the resonator and, subsequently, read out its state, and has been used previously to prepare and detect photon number states (Fock states). Using a generalization of this scheme by Law and Eberly, we can now create arbitrary quantum states of the photon field with up to approximately 10 photons: the deterministic synthesis of such states can be considered as the quantum version of a digital to analog converter. The states are analyzed by directly mapping out the corresponding Wigner function, which is the phase-space equivalent to the density matrix.

1201 Physics Building
College Park, MD 20742

Subscribe to A Quantum Bit 

Quantum physics began with revolutionary discoveries in the early twentieth century and continues to be central in today’s physics research. Learn about quantum physics, bit by bit. From definitions to the latest research, this is your portal. Subscribe to receive regular emails from the quantum world. Previous Issues...

Sign Up Now

Sign up to receive A Quantum Bit in your email!

 Have an idea for A Quantum Bit? Submit your suggestions to jqi-comm@umd.edu