Achieving $10^{-5}$ level relative intensity crosstalk in optical holographic qubit addressing via a double-pass digital micromirror device

Holographic beam shaping is a powerful approach for generating individually addressable optical spots for controlling atomic qubits, such as those in trapped-ion quantum processors. However, its application in qubit control is limited by residual intensity crosstalk at neighboring sites and by a nonzero background floor in the far wings of the addressing beam, leading to accumulated errors from many exposed qubits. Here, we present an all-optical scheme that mitigates both effects using a single digital micromirror device (DMD) operated in a double-pass configuration, in which light interacts with two separate regions of the same device. In the first pass, one region of the DMD is placed in a Fourier plane and implements a binary-amplitude hologram for individual addressing, while in the second pass a different region serves as a programmable intermediate image-plane aperture for spatial filtering. By multiplexing the Fourier-plane hologram to include secondary holograms, we generate weak auxiliary fields that interfere destructively with unwanted light at selected sites, while image-plane filtering suppresses the residual tail at larger distances. Together, these techniques maintain relative intensity crosstalk at or below $10^{-5}$ ($-50,\mathrm{dB}$) across the full field of view relevant for qubit addressing, and further reduce the far-wing background to approximately $10^{-6}$ at large distances from the addressed qubit, approaching the detection limit. These results provide a compact, DMD-based solution for low-crosstalk optical holographic qubit addressing that is directly applicable to trapped ions and other spatially ordered quantum systems.

💡 Research Summary

This paper presents a significant advancement in optical holographic techniques for individually addressing qubits in quantum processors, specifically targeting trapped-ion systems. The primary challenges in this field have been residual intensity crosstalk at neighboring qubit sites and a non-zero background illumination floor in the far field, both of which lead to accumulated errors that hinder scalability.

The authors’ innovative solution centers on a novel, all-optical scheme that uses a single Digital Micromirror Device (DMD) in a double-pass configuration. In this setup, light interacts with two distinct regions of the same DMD. In the first pass, one region (FP1) operates in a Fourier plane, displaying a binary-amplitude hologram calculated via an Iterative Fourier Transform Algorithm (IFTA) to generate the primary addressing beam. To suppress crosstalk at specific nearby locations, the team introduces “multiplexed Fourier holograms.” This involves replacing a small subsection of the primary hologram with a secondary binary grating hologram, engineered to produce a weak auxiliary optical field at a chosen off-target site. By precisely tuning the amplitude and phase of this auxiliary field, destructive interference with the unwanted light from the primary beam is achieved, creating a local intensity minimum. This technique demonstrated an average improvement of about 5 dB, reducing crosstalk to approximately -48 dB at a distance of 4 beam widths (w) from the target.

The second pass through the DMD addresses the problem of the far-wing background. The light is relayed to a different region of the DMD (IP1), which lies in an intermediate image plane. This region functions as a programmable reflective aperture. By selectively turning mirrors “ON” only in the area corresponding to the core of the desired beam, the system acts as a spatial filter, blocking the weak, diffuse tails of the beam at larger distances. This image-plane filtering effectively truncates the beam profile, suppressing the background floor. Measurements showed that with this filtering, relative intensity crosstalk falls below -50 dB at distances greater than about 14w and approaches -60 dB (around 10^-6) beyond 30w from the addressed qubit.

By integrating these two complementary techniques—multiplexed Fourier holograms for local crosstalk cancellation and intermediate image-plane filtering for global background suppression—onto a single, compact DMD platform, the research achieves a comprehensive solution. The system maintains relative intensity crosstalk at or below the 10^-5 level (-50 dB) across the entire field of view relevant for qubit addressing. This performance level meets a critical requirement for high-fidelity quantum gate operations and scalable quantum circuit execution. The use of a fast, binary DMD further makes this approach promising for dynamic and reconfigurable addressing patterns needed in advanced quantum computing applications, directly benefiting trapped-ion and other spatially ordered quantum systems.