What if dark matter and dark energy are the medium through which photons and gravitational waves reach us? In our new work, we take a materials-science perspective — and characterize the macroscopic properties of these mysterious cosmic substances [1/25].

It’s been a real pleasure collaborating with physicists outside cosmology on this project. Huge thanks to Alessio, Ana, and Michał for the countless hours of discussions and the effort to bridge quantum information and cosmology 🌌⚛️[20/20].

. we’re effectively stuck probing a classical probability distribution — one that hides clear quantum signatures [19/20].

Even though the quantum states of cosmological inhomogeneities may show strong non-classical traits, our limited observational access during inflation means. [18/20].

This tension highlights a key puzzle about quantum perturbations in the early universe [17/20].

It would require accessing the decaying mode of inflationary perturbations — something that’s extremely challenging and may still fall short of true optimality [16/20].

But — and it’s a big but — this measurement is far beyond the reach of current observations [15/20].

The conclusions are twofold: first, there is an optimal measurement strategy that can constrain the tensor-to-scalar ratio extremely well [14/20].

Our main result: there is a huge gap between the classical and quantum Fisher information — one that grows exponentially with the duration of inflation. [13/20].

For concreteness, we focus on the tensor-to-scalar ratio — a key observational target in upcoming experiments (e.g. @SimonsObs) [12/20].

To understand how much information we lose due to limited access to early-universe data, we contrast the quantum Fisher information — the best-case scenario — with the classical Fisher information extracted from measurements of the Gaussian curvature perturbations alone [11/20].

This limited observational access makes it much harder to reconstruct the quantum state produced by inflation [10/20].

Key features — like non-Gaussianities in scalar perturbations, primordial gravitational wave statistics, or momentum correlations — are either weakly constrained or not measured at all [9/20].

Unfortunately, our window into the early Universe is still pretty narrow [8/20].

It sets the ultimate limit on how precisely we could measure a parameter — if we had ideal access to the early Universe’s quantum state [7/20].

So how do we approach this? We bring in quantum metrology — specifically, the quantum Fisher information — and apply it to the state of cosmological fluctuations right after inflation [6/20].

This raises two deep questions:.· How well can we infer a given parameter?.· What’s the best way to do it? [5/20].

I've always found it wild that we just collect photons with telescopes — and somehow extract things like the dark matter abundance or the Universe’s expansion rate [4/20].

In cosmology, this process shapes nearly everything we know about the Universe: its composition, its history, its fate [3/20].

Estimating the values of a model’s parameters — what we call parameter inference — lies at the heart of scientific discovery [2/20].

What’s the best way to extract information about the early universe? In our new paper, we tackle this classic cosmology problem using tools from quantum information theory🧵[1/20] #Physics #Cosmology #Quantum @Cambridge_Uni.