Method and structure to isolate a qubit from the environment

#1. Field of the Invention

#The present invention generally relates to a quantum computer. More specifically, to a method and structure which locates a qubit at a node of a qubit basic operational frequency on control and readout transmission lines, so as to minimize decoherence caused by these control and readout functions.

#2. Description of the Related Art

#The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of an exemplary embodiment of the invention with reference to the drawings, in which:

#FIG. 1 shows one exemplary configuration 100 for coupling to a qubit in accordance with the principles of the present invention;

#FIG. 2 illustrates a second exemplary configuration 200 for coupling to a current-based qubit, using a superconducting microstrip transmission line with a shorted end;

#Referring now to the drawings, and more specifically, FIGS. 1-4, the present invention provides a method of decoupling a qubit from the environment at a frequency that has the largest effect in causing decoherence in the qubit (e.g., frequency F01), while at the same time coupling the qubit at most other frequencies, such as the frequencies over which the qubit is operated and measured.

#For a qubit, the noise from the environment will usually vary as a function of frequency. In the normal operation of a qubit, the environmental noise at two specific frequencies is important. The most important frequency (e.g., the noise that decoheres the qubit the most) is noise at the basic operational frequency of the qubit, referred to as the “F01” frequency.

#In other words, F01 is the frequency difference between the “0” (e.g., the lowest energy state) and the “1” (e.g., the second lowest energy state of the qubit). However, the present invention should not be viewed as limited to the F01 frequency, since some qubit designs operate at other frequencies, such as “F12”. Thus, the present invention includes a broader concept in which details may vary from one qubit design to another and frequency “F01” is exemplarily used herein for the sake of discussion.