What is the Ornstein–Uhlenbeck process, and why use it as a baseline?

The Ornstein–Uhlenbeck (OU) process models a quantity that fluctuates randomly but is continually pulled back toward a long-term mean — Quantustik uses it as the honest baseline its quantum models must beat.

Why Quantustik uses OU as an honest baseline

Sentiment gauges like the Fear & Greed Index are natural OU candidates: extreme readings historically tend to normalize. Quantustik fits an OU model to these series specifically to serve as the honest, simple baseline its more elaborate quantum-inspired models must beat — if a fancier model can't outperform a well-fit OU baseline on out-of-sample data, that's a signal the extra complexity isn't earning its keep.

Live example: the CNN Fear & Greed Index currently reads 38 (fear) — an Ornstein–Uhlenbeck baseline treats this as a mean-reverting series, so an extreme reading carries an implicit pull back toward its long-run average. See the Fear & Greed model page for how the OU baseline compares to Quantustik's fancier models on this exact series.

OU vs. the quantum-inspired models

Where OU always pulls toward one fixed equilibrium, the Schrödinger-based approach can fit a potential with more than one basin, allowing for genuinely multi-modal forecasts the single-equilibrium OU process cannot represent.

Frequently asked questions

Is the Ornstein–Uhlenbeck process the same as AR(1)?

In discrete time, yes — the OU process is the continuous-time analogue of the AR(1) autoregressive model.

Why compare quantum-inspired models to something this simple?

Because a simple, well-understood baseline is the fairest test: if a more complex model can't beat a properly-fit OU process on out-of-sample data, the added complexity isn't earning its keep.

Does OU work for stock prices too, not just sentiment?

It can, but is a better fit for series with a stable long-run mean, like a bounded sentiment index, than stock prices, which can trend for extended periods.

See it on a ticker

AAPL analysis shows this metric in context, or browse all S&P 500 tickers.

Related terms

Educational research only — not investment advice.