Revealing the magic in hybrid quantum systems
Quantum technologies rely on more than just entanglement. Another, less well-known ingredient is non-stabiliserness, often called magic The post Revealing the magic in hybrid quantum systems appeared first on Physics World .
Quantum technologies have long been celebrated for their potential to revolutionize computing, cryptography, and communication. While entanglement is often highlighted as a key resource, there is another, less well-known property that plays a crucial role: non-stabiliserness, often referred to as "magic." This property determines whether a quantum system can outperform even the fastest classical supercomputer. Until now, scientists could quantify magic in systems of qubits, but not in systems of bosons such as photons or hybrid devices of coupled bosons and spins, like those used in real quantum hardware.
In a groundbreaking new study, a team of researchers from Taiwan and Japan has proposed the first unified way to measure magic in systems that combine both spins and bosons. These hybrid platforms are ubiquitous in modern quantum computing, appearing in superconducting circuits, trapped ion quantum processors, and other architectures. However, the quantum resources inside them have remained difficult to identify.
The team's new framework uses the shape of a quantum state in phase space to define a family of magic entropies that apply cleanly to qubits, bosons, and crucially, the interactions between them. This breakthrough allows researchers to quantify the unique quantum advantages of hybrid systems, which have been at the forefront of quantum computing advancements.
To test the idea, the researchers examined the Dicke model, a paradigmatic system in which many spins couple to a single light field. As the system approaches a superradiant phase transitionтАФa dramatic collective reorganisationтАФthe shared non-classical behaviour across both spins and photons (the hybrid magic) peaks at this transition. This provides another way to identify the critical point, alongside familiar tools such as entanglement.
Another interesting result is that, in the finite systems studied here, the quantum magic in the spin sector increases sharply, while the bosonic magic saturates to a finite value. This contrast suggests that these measures capture different aspects of the quantum state. Understanding these distinctions is essential for optimizing quantum systems and harnessing their full potential.
The team also analysed how magic evolves dynamically in the JaynesтАУCummings model, where a single spin and a single photon exchange energy. As the two systems swap excitations, magic flows back and forth, and exhibits different behaviours for bosonic and spin parts. This dynamic interplay provides a picture of how computational power migrates through a quantum device in real time.
As quantum computers grow more complex, scientists and engineers need reliable ways to quantify and characterize the unique properties of hybrid quantum systems. The researchers' framework offers a powerful tool for understanding and optimizing these systems, paving the way for more efficient and powerful quantum technologies.
In conclusion, the ability to measure magic in hybrid quantum systems opens up new avenues for studying and harnessing the unique quantum advantages of these platforms. By providing a unified framework for quantifying this elusive property, the researchers have taken a significant step forward in the development of practical quantum technologies. As the field continues to evolve, understanding and optimizing the magic in hybrid systems will be key to unlocking the full potential of quantum computing and other quantum applications.
