quantum-limited-subdiffraction-telescopy

name	quantum-limited-subdiffraction-telescopy
description	Quantum-limited subdiffraction telescopy using genuine multi-telescope interference. Proves pairwise measurements insufficient for higher-order image moment estimation at quantum limit. Constructs array-SPADE measurements attaining optimal QFI scaling up to finite-array cutoff. Applicable to quantum metrology, astronomical imaging, quantum network telescopy, and spatial-mode demultiplexing.
metadata	{"arxiv_id":"2606.27276","published":"2026-06-25","authors":"Yujie Zhang, Yunkai Wang, Wilson Wu, Thomas Jennewein","tags":["quantum","information-theory","telescopy","quantum-fisher-information","SPADE","multi-telescope","interferometry","imaging"]}

Quantum-Limited Subdiffraction Telescopy via Multi-Telescope Interference

Overview

Conventional stellar interferometry reconstructs incoherent sources from pairwise mutual coherences. For generic image-moment estimation, pairwise measurements are not sufficient for quantum-limited subdiffraction imaging.

Core Theory

Quantum Fisher Information Scaling

For an N-telescope array observing weak incoherent light from a generic extended source:

• QFI scaling of image moments: derived up to cutoff 2N-2
• Pairwise measurements attain full-array QFI scaling only up to second order
• Higher-order moment estimation at the quantum limit requires genuinely multi-telescope interference

Key Result

Measurement Type	Max Order Attaining Full QFI
Telescope pairs	2nd order
Full N-array	2N-2

The gap between pairwise and full-array capability grows with array size.

array-SPADE Construction

Inspired by spatial-mode demultiplexing (SPADE) from single-aperture subdiffraction imaging:

1. Construct array-SPADE measurements
2. Attain optimal QFI scaling up to finite-array cutoff
3. Embeddable in ancilla- and memory-assisted quantum-network architectures for long-baseline telescopy

Methodology

When Pairwise Is Insufficient

1. Determine the order of image moment to estimate
2. If order > 2, pairwise coherence measurements lose QFI scaling
3. Design multi-telescope interference measurement

array-SPADE Implementation Steps

1. Map each telescope's optical mode to the array-SPADE basis
2. Perform joint measurement across all N modes simultaneously
3. Extract image moments up to order 2N-2
4. Use ancilla-assisted protocols for long-baseline operation

Pitfalls

• Pairwise sufficiency misconception: Many papers assume pairwise coherence measurements are sufficient for arbitrary resolution enhancement — this paper proves they are not for higher-order moments
• Memory requirement: Multi-telescope interference requires quantum memory/ancilla for long baselines where light arrives asynchronously
• Finite cutoff: QFI scaling has fundamental cutoff at 2N-2 for N telescopes — cannot estimate arbitrarily high-order moments regardless of measurement sophistication

Related Papers

• SPADE (single-aperture spatial-mode demultiplexing)
• Quantum Fisher Information estimation under decoherence
• Multi-mode entangling-gate synthesis in trapped-ion systems (2606.27266)

Activation

Keywords: quantum telescopy, subdiffraction imaging, quantum Fisher information, array-SPADE, multi-telescope interference, stellar interferometry, image-moment estimation, quantum-limited resolution, spatial-mode demultiplexing