A new control method for robust quantum information processing suited for integrated photonics.

The advance of quantum technologies has given rise to an immediate need for feasible methods for precise state preparation and accurate state transfer in qubit platforms. In recent years, integrated photonic circuits have emerged as a strong contender for quantum information processing (QIP) hardware due to their scalability and on-chip integration capacity. However, unavoidable fabrication errors lead to a significant decrease in the fidelity of light transfer and limit their integration in QIP applications.
The new detuning-modulated composite pulses (CP) technique is advantageous for maintaining high-fidelity quantum operations in integrated circuits or any qubit architecture prone to fabrication errors. CPs are a series of pulses with different areas and/or phases that implement accurate and robust quantum gates on two-level systems characterized by a complex coupling parameter and detuning. Thus, quantum operations designed for detuning-modulated CPs are inherently stable to all systematic errors, such as coupling strength, pulse duration and detuning errors (phase mismatch), seen in Fig. I (a-c). These are the first CPs that employ real-valued control knobs.
Potential Applications
A broad variety of final products that will be utilized in the field of quantum computation should be expected in light of this invention. Scalable components with high fidelity and robustness to fabrication and systematic errors are very desirable products for commercial use in integrated photonics design, efficient switches, broadband detectors and also crystals for high harmonic generation. One such component that we have demonstrated is an efficient coupler, seen in Fig. II and Fig. III. In this physical configuration, the coupling is set by the separation between two waveguides, the detuning (phase mismatch) is governed by the difference in the geometry of each waveguide and the pulse area is determined by the length of each composite segment.
Detuning-modulated CPs allow for minimal pulse overhead, which translates to shorter component lengths. Thus, functionality does not depend strongly on the total length, allowing for compact, minimal-footprint devices. Moreover, detuning-modulated CPs allow for straightforward scaling for any arbitrary N-piece sequence, enabling for scalable components.