QuCSI

The classical-quantum divergence of complexity in the ising spin chain (Quantum 1, 25)

Can quantum information fundamentally change the way we perceive what is complex? In our article, “The classical-quantum divergence of complexity in the Ising spin chain,” we generalize a widely-used measure of complexity – the statistical complexity – to the quantum regime. Statistical complexity quantifies the minimal classical information we must store about a process to ... Read moreThe classical-quantum divergence of complexity in the ising spin chain (Quantum 1, 25)

Thermodynamics of Complexity and Pattern Manipulation (Physical Review E 95 4, 042140)

At the heart of complexity and complex systems is the manipulation of patterns – predictable structures – using an internal memory, but the exact structure of this memory is not uniquely defined. In this article,  we consider the thermodynamics involved in this manipulation, such as by living things which exploit patterns in their surroundings, and ... Read moreThermodynamics of Complexity and Pattern Manipulation (Physical Review E 95 4, 042140)

Overarching framework between Gaussian quantum discord and Gaussian quantum illumination (Physical Review A 95, 2, 022333)

Quantum illumination is a fascinating protocol that allows the improved sensing of distant objects with entanglement - even when the object is encased in so much noise that all entanglement is destroyed. Previously, we were able to show that this phenomenon is related to quantum discord, a more robust notion of quantum correlations. In this ... Read moreOverarching framework between Gaussian quantum discord and Gaussian quantum illumination (Physical Review A 95, 2, 022333)

Using quantum theory to simplify input–output processes (npj Quantum Information 3, 6)

Can a quantum goldfish exhibit more complex behaviour than a classical dolphin? In omplexity science, the complexity of an input-output process – a system that reacts differently when supplied with different environmental stimuli – can be quantified by the minimal memory needed to reproduce the process’s observed behaviour. This reflects the intuition that a goldfish ... Read moreUsing quantum theory to simplify input–output processes (npj Quantum Information 3, 6)

Experimentally modelling stochastic processes with less memory by the use of a quantum processor (Science Advances Vol 3, No. 2)

When it comes to studying transportation systems, stock markets and the weather, quantum mechanics is probably the last thing to come to mind. We have just demonstrated a proof of principle experiment that shows when it comes simulating such complex processes in the macroscopic world, quantum mechanics can provide an unexpected advantage – by drastically ... Read moreExperimentally modelling stochastic processes with less memory by the use of a quantum processor (Science Advances Vol 3, No. 2)

Thermodynamical cost of some interpretations of quantum theory (Phys. Rev. A 94, 052127)

The interpretation of quantum theory is one of the longest-standing debates in physics. But is there a way to favor one over another using the rules of Thermodynamics? In this work, Adam Cabello and colleagues worked with us to see if the tools of complexity can provide an answer. The answers are preliminary, but appears ... Read moreThermodynamical cost of some interpretations of quantum theory (Phys. Rev. A 94, 052127)

Quantum Processes Which Do Not Use Coherence (Phys. Rev. X 6, 041028)

One of the core tenets of quantum theory is that systems can exist in superpositions of different states, now often termed “coherence.” However, only recently have scientists formulated a rigorous mathematical characterization of this property, work that has paved the way for many studies of coherence as a fundamental quantity. A crucial part of quantum ... Read moreQuantum Processes Which Do Not Use Coherence (Phys. Rev. X 6, 041028)

Unbounded memory advantage in stochastic simulation using quantum mechanics (New Preprrint)

We know that quantum mechanics are save memory in modelling stochastic processes, but how great can this advantage be and does it scale? In our latest work, we study a family of processes where the memory advantage does indeed scale, and very impressively at that. In particular, as the amount of classical memory required to ... Read moreUnbounded memory advantage in stochastic simulation using quantum mechanics (New Preprrint)

Fragile states are better for quantum metrology (New Preprint)

We knows that quantum information allows us to estimate certain unknown parameters to precisions beyond classical limits. The archetypal example, being the use of the NOON state - a superposition of N photons in either Mode A or Mode B - for phase estimation. Unfortunately, this same state is very fragile - if you accidentally ... Read moreFragile states are better for quantum metrology (New Preprint)

Power of one qumode for quantum computation (Phys. Rev. A 93, 040304)

Hybrid quantum computation - where one makes simultaneous use of continuous and discrete variables at the same time, is a interesting variant of standard quantum computation. In this paper, we proposed a version of hybrid quantum computers that involved a single squeezed state, together with a reservoir of completely mixed states. This is reminiscent of ... Read morePower of one qumode for quantum computation (Phys. Rev. A 93, 040304)