Quantum Dot Multiplexed Barcode Imaging

Barcode Encoding

Spectral channels (QD colors)

Intensity levels per channel

Detector noise / crosstalk 15%

Channel Emission Colors

Live Decode

Code space capacity

Beads imaged

Decode accuracy

100.0%

Correct

Misread

How it works

Each bead is doped with a fixed ratio of C different quantum-dot emission colors (spectral channels), each dosed at one of L discrete intensity levels. A detector reads the bead's spectrum, normalizes each channel to a fraction 0…1, and classifies the reading against every valid code by nearest-neighbour distance:

code capacity  N = L^C − 1   (excludes the "all-off" blank code)
channel level  v_k ∈ {0, 1, …, L−1},  k = 1…C
measured       m_k = v_k/(L−1) + noise,  noise ~ N(0, σ²)
decoded code   argmin over all codes of  Σ_k (m_k − code_k)²

This is the combinatorial optical-coding scheme used in real multiplexed bioassays (Han, Gao & Nie, Nature Biotechnology 2001): instead of one probe per test tube, a single pool of beads — each carrying its own quantum-dot barcode — can report on dozens of targets simultaneously, decoded by the ratio of colors a detector sees, not by a single wavelength.

Channels / Levels — set L and C; capacity N = L^C − 1 grows fast (more distinguishable barcodes), but packs codes closer together in intensity space.
Detector noise — Gaussian scatter added to every channel reading before decoding, modelling photon shot noise and spectral crosstalk between adjacent QD emission peaks.
New Code Set — re-assigns random true barcodes to all beads. Rescan Now — takes one fresh noisy reading of the existing beads (the detector also rescans continuously).
Inner sphere = the bead's true spectral color (ground truth). Outer glow = the detector's verdict — green when the nearest-code decode matches the true barcode, red when noise pushed it into a neighbouring code's territory.

Correctly decoded Misread barcode

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