Lecture 9

How many measurements are needed at minimum to reconstruct the density matrix of a single qubit state?

• 1

• 2

• 3

• 4

The capacitive coupling between two qubits is diagonal.

• True

• False

What is the disadvantage of quantum bus mediated coupling?

• Qubits cannot be placed far away

• Coupling is usually too weak

• Coupling cannot be turned effectively off

• Qubits can be exposed to dephasing during manipulation.

The CPhase gate uses the 0,1-2,2 avoided crossing for manipulation

• True

• False

Which one is not always true for a density matrix?

• The trace is 1.

• The trace of the square of the matrix is 1.

• It is Hermitian.

• It is positive

Entangled states cannot be written as a tensor product

• True

• False

CPhase gate cannot be used to make entangled states.

• True

• False

On the above image coupling is realized between qubits (with coupling resonators).

• Db and At is coupled via a bus

• Db and Dt is coupled via a bus

• Db and Ab is coupled via a bus

• Dt and Ab is coupled via a bus

High gate fidelities can also be realized with tunable frequency transmons.

• True

• False

For a CPhase gate how big is the process tomography matrix?

• 2x2

• 4x4

• 8x8

• 16x16