  Two-level systems (TLS) are the major source of dephasing of spin qubits in
numerous quantum computing platforms. In spite of much effort, it has been
difficult to substantially mitigate the effects of this noise or, in many
cases, to fully understand its physical origin. We propose a method to make
progress on both of these issues. When an oscillating field is applied to a
TLS, stochastic resonance can occur and the noise spectrum is moved to higher
frequencies. This shift in the TLS noise spectrum will increase the dephasing
times of the qubits that they influence. Furthermore, the details of this
effect depend on the physical properties of the noise sources. Thus one can use
qubit spectroscopy to investigate their physical properties, specifically the
extent to which the TLS themselves possess quantum coherence. We find that it
should be possible to determine the dephasing rate and the energy level
separation of the TLS themselves in this way.
