Periodic Reporting for period 1 - ATOMAG (Exploiting pseudo-gauge fields for novel light-matter interfaces)
Berichtszeitraum: 2022-08-01 bis 2024-11-30
Programable tweezer arrays with highly-coherent Rydberg interactions have emerged as one of the leading platforms for quantum information processing and quantum simulation of many-body phenomena in various short-range spin models. In contrast, atom-light interfaces exhibit fundamentally different characteristics. They are inherently open quantum systems and typically suffer from uncontrolled dissipation, which results in a substantial loss of quantum information and renders it difficult to realize strongly-correlated quantum states. Moreover, photons often mediate long-range or even infinite-range interactions between atoms, which means the dynamics if often well captured by mean-field or semi-classical techniques (e.g. Dicke superradiance). To drive atom-light interfaces toward greater complexity, it is essential to identify mechanisms that mitigate unwanted dissipation and to evade mean-field behaviour.
ATOMAG is an interdisciplinary project that aims to unveil novel atom-light interfaces for efficient quantum information processing and the exploration of strongly-correlated many-body phenomena. By bridging these fields, ATOMAG aims to push the boundaries of the emerging field of many-body quantum optics, offering new insights and potential breakthroughs in quantum science.
ATOMAG is an interdisciplinary project that aims to unveil novel atom-light interfaces for efficient quantum information processing and the exploration of strongly-correlated many-body phenomena. By bridging these fields, ATOMAG aims to push the boundaries of the emerging field of many-body quantum optics, offering new insights and potential breakthroughs in quantum science.
Below we highlight two main achievements from ATOMAG, one focused on efficient atom-light interfaces for quantum information processing and the other focused on generating exotic many-body states.
Project 1: Selective radiance in super-wavelength atomic arrays
A new generation of efficient atom-light interfaces has recently been proposed based on the notion of selective radiance, where destructive wave interference is utilized as resource to suppress emission into unwanted optical modes. It is generally assumed that this strategy requires dense atomic arrays with sub-wavelength lattice constants. While a 2D super-wavelength array is a very poor atom-light interface, due to photons being scattered into multiple diffraction orders, we demonstrate that one can restore the selective radiance by stacking multiple 2D layers. Using an idealized model, we identify a range of super-wavelength mirror configurations that selectively radiate into the target specular mode at an enhanced rate, while scattering into all diffraction orders is eliminated through interlayer destructive interference. Guided by this intuition, we show that realistic super-wavelength arrays can almost perfectly reflect a weak classical beam on resonance, and also be functionalized into efficient quantum memories for single photons. In particular, by locally optimizing the atomic positions we show that one can in principle achieve errors on the order of ~1% with only around ~100 atoms.
Project 2: Emergence of quantum spin liquids from global atom-cavity interactions
Conventional cavity QED phenomena, such as Dicke superradiance, are typically dominated by the semi-classical behaviour of the ensemble's collective spin (S ~ N/2). To move towards complexity, we have demonstrated that global cavity-induced fluctuations can melt classical Ising magnets into quantum spin liquids (QSLs) that exhibit fractionalized excitations and emergent gauge fields. Our key idea is to utilize a strong cavity to project the system into the global singlet sector (S = 0), thereby evading collective-spin physics. By introducing short-range Ising perturbations, such as those arising from Rydberg interactions, the low-energy states map exactly onto the singlet sector of the corresponding short-range Heisenberg model, which can host a variety of QSLs. Focusing on the J1-J2 square lattice model as a paradigmatic example, we show that the cavity initially squeezes the classical antiferromagnetic states by generating EPR-like entanglement between sublattices, and then magnon-magnon interactions melt the classical order into the candidate QSL ground state of the Heisenberg model.
Project 1: Selective radiance in super-wavelength atomic arrays
A new generation of efficient atom-light interfaces has recently been proposed based on the notion of selective radiance, where destructive wave interference is utilized as resource to suppress emission into unwanted optical modes. It is generally assumed that this strategy requires dense atomic arrays with sub-wavelength lattice constants. While a 2D super-wavelength array is a very poor atom-light interface, due to photons being scattered into multiple diffraction orders, we demonstrate that one can restore the selective radiance by stacking multiple 2D layers. Using an idealized model, we identify a range of super-wavelength mirror configurations that selectively radiate into the target specular mode at an enhanced rate, while scattering into all diffraction orders is eliminated through interlayer destructive interference. Guided by this intuition, we show that realistic super-wavelength arrays can almost perfectly reflect a weak classical beam on resonance, and also be functionalized into efficient quantum memories for single photons. In particular, by locally optimizing the atomic positions we show that one can in principle achieve errors on the order of ~1% with only around ~100 atoms.
Project 2: Emergence of quantum spin liquids from global atom-cavity interactions
Conventional cavity QED phenomena, such as Dicke superradiance, are typically dominated by the semi-classical behaviour of the ensemble's collective spin (S ~ N/2). To move towards complexity, we have demonstrated that global cavity-induced fluctuations can melt classical Ising magnets into quantum spin liquids (QSLs) that exhibit fractionalized excitations and emergent gauge fields. Our key idea is to utilize a strong cavity to project the system into the global singlet sector (S = 0), thereby evading collective-spin physics. By introducing short-range Ising perturbations, such as those arising from Rydberg interactions, the low-energy states map exactly onto the singlet sector of the corresponding short-range Heisenberg model, which can host a variety of QSLs. Focusing on the J1-J2 square lattice model as a paradigmatic example, we show that the cavity initially squeezes the classical antiferromagnetic states by generating EPR-like entanglement between sublattices, and then magnon-magnon interactions melt the classical order into the candidate QSL ground state of the Heisenberg model.
Below we explain how these results go beyond the current state of the art and highlight their potential impact:
Project 1: Selective radiance in super-wavelength atomic arrays
Within the quantum optics community, it is widely assumed that selective radiance requires dense atomic arrays with sub-wavelength lattice constants. Achieving such configurations generally involves loading ultracold atoms into an optical lattice to form a 2D Mott insulator. A tantalizing alternative would be to utilize tweezer array technology since it offers faster repetition rates for quantum optics operations, but unfortunately the diffraction limit forces tweezer separation to be super-wavelength. However, we have established that sub-wavelength spacing is not a fundamental requirement, potentially enabling tweezer arrays to be deployed as an efficient atom-light interface. In fact, multilayer tweezer arrays have already been demonstrated in proof-of-principle experiments.
Project 2: Emergence of quantum spin liquids from global atom-cavity interactions
The recent integration of tweezer arrays into high-finesse cavities has opened a compelling new frontier in quantum science. From the perspective of quantum information processing, the cavity-enhanced atom-light coupling improves measurements capabilities, facilitates the connection of distant quantum processors, and enables long-range entangling gates via cavity-mediated interactions. However, the new opportunities that might emerge for exploring strongly-correlated many-body phenomena has remained largely unexplored. Our results highlight that rich many-body phases can emerge from the competition between long-range and short-range interactions, which can be explored in this new generation of tweezer-cavity interfaces. We are currently collaborating with several world-leading experimental groups to explore the potential for realizing quantum spin liquids in cavity QED set-ups.
Project 1: Selective radiance in super-wavelength atomic arrays
Within the quantum optics community, it is widely assumed that selective radiance requires dense atomic arrays with sub-wavelength lattice constants. Achieving such configurations generally involves loading ultracold atoms into an optical lattice to form a 2D Mott insulator. A tantalizing alternative would be to utilize tweezer array technology since it offers faster repetition rates for quantum optics operations, but unfortunately the diffraction limit forces tweezer separation to be super-wavelength. However, we have established that sub-wavelength spacing is not a fundamental requirement, potentially enabling tweezer arrays to be deployed as an efficient atom-light interface. In fact, multilayer tweezer arrays have already been demonstrated in proof-of-principle experiments.
Project 2: Emergence of quantum spin liquids from global atom-cavity interactions
The recent integration of tweezer arrays into high-finesse cavities has opened a compelling new frontier in quantum science. From the perspective of quantum information processing, the cavity-enhanced atom-light coupling improves measurements capabilities, facilitates the connection of distant quantum processors, and enables long-range entangling gates via cavity-mediated interactions. However, the new opportunities that might emerge for exploring strongly-correlated many-body phenomena has remained largely unexplored. Our results highlight that rich many-body phases can emerge from the competition between long-range and short-range interactions, which can be explored in this new generation of tweezer-cavity interfaces. We are currently collaborating with several world-leading experimental groups to explore the potential for realizing quantum spin liquids in cavity QED set-ups.