The single-photon Raman interaction has emerged as a promising tool for deterministic photon subtraction, acting as a photon-activated switch in which the first arriving photon renders the system transparent to subsequent photons. Here, we employ the input-output formalism to perform a single-photon transport analysis within a photon subtractor consisting of a three-level quantum emitter coupled to a bimodal cavity-waveguide system. The analysis provides the frequency response of the system and reveals how it is affected by the key physical parameters of the cavity modes, such as coupling strengths and decay rates. We utilize these results to calculate the probability of successful photon subtraction from pulses of different temporal shapes, durations, and carrier frequencies. Subsequent analysis combines the input-output formalism with the quantum trajectory method to numerically verify the analytical findings as well as to assess the impact of photon number of the input pulse on the subtractor's performance. Our findings highlight the single-photon model's capability in predicting the system's response to multiphoton inputs in the pulsed regime as well as its potential utility in the design of efficient single-photon subtractors.
Abstract We propose a scheme for deterministic single photon subtraction based on Single Photon Raman Interaction (SPRINT) with a three-level quantum emitter coupled to a chiral waveguide and present an analytical and numerical study of its feasibility. We show that single photon subtraction probability for pulsed input light in a coherent or a Fock state can approach unity in the ideal limit and discuss the potential of various reported quantum emitter-waveguide platforms as candidates for experimental realization of our scheme. The use of chiral slow-light photonic crystal waveguides coupled to Λ -type emitters can perform efficient photon subtraction. While integrating cold atoms to such systems remains technically challenging, solid-state emitters offer a potentially practical path to realize such photon subtraction.
Developing fault-tolerant quantum processors with error correction demands large arrays of physical qubits whose key performance metrics (coherence times, control fidelities) must remain within specifications over both short and long timescales. Here we investigated the temporal stability of subtractively fabricated CMOS-compatible superconducting transmon qubits. During a single cooldown and over a period of 95 hours, we monitored several parameters for 8 qubits, including coherence times
T1 and
T2∗, which exhibit fluctuations originating primarily from the interaction between two-level system (TLS) defects and the host qubit. We also demonstrate that subtractively-fabricated superconducting quantum devices align with the theoretical predictions that higher mean lifetimes
T1 correspond to larger fluctuations. To assess long-term stability, we tracked two representative qubits over 10 cooldown cycles spanning more than one year. We observed an average total downward shift in both qubit transition frequencies of approximately 61 MHz within the thermal cycles considered. In contrast, readout resonator frequencies decreased only marginally. Meanwhile,
T1 exhibits fluctuations from cycle to cycle, but maintains a stable baseline value.