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ground of a wire of any usable length would be much smaller than that of the
qubit, effectively shorting the coupling.
The current proposal by the involved
groups consists of placing the qubits inside the cavity of a coplanar waveguide
resonator [Majer et al., 2007]. Coupling only via resonant excitations in the resonator
then allows for long-distance communication between several qubits. The
lack of frequency tuneability of the charge qubit makes this method of coupling
fairly complex.
2.3.4 Readout
There are four primary types of readout schemes that differ in two binary
properties.
The readout can be either single-shot or non-single-shot. Single-shot readout
projects every qubit involved in the experiment into the | 0 〉 or | 1 〉 state and
returns one specific final output state like | 0110001 〉 for each experimental run.
Non-single-shot readout schemes return a measurement that is an analog function
of the possible output states. A simple example could consist of a measurement of
the total energy stored in all qubits, which is proportional to the number of qubits
in the | 1 〉 state. Even though single-shot readout is not required for quantum
computation, it is highly desirable as it yields results that don’t require extensive
post-processing or calibration to extract the actual state probabilities.
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