arXiv subjects

Tanjung Krisnanda

Publications and source records attributed to Tanjung Krisnanda.

26 records · Page 2Linked to original sources

arXiv2021

Room Temperature Light-Mediated Long-Range Coupling of Excitons in Perovskites

Perovskites have been the focus of attention due to their multitude of outstanding optoelectronic properties and structural versatility. Two-dimensional halide perovskite such as (C_6H_5C_2H_4NH_3)_2PbI_4, or simply PEPI, forms natural multiple quantum wells with enhanced light-matter interactions, making them attractive systems for further investigation. This work reports tunable splitting of exciton modes in PEPI resulting from strong light-matter interactions, manifested as multiple dips (modes) in the reflection spectra. While the origin of the redder mode is well understood, that for the bluer dip at room temperature is still lacking. Here, it is revealed that the presence of the multiple modes originates from an indirect coupling between excitons in different quantum wells. The long-range characteristic of the mediated coupling between excitons in distant quantum wells is also demonstrated in a structure design along with its tunability. Moreover, a device architecture involving an end silver layer enhances the two excitonic modes and provides further tunability. Importantly, this work will motivate the possibility of coupling of the excitonic modes with a confined light mode in a microcavity to produce multiple exciton-polariton modes.

cond-mat.mtrl-sci↗

arXiv2021

Creating and concentrating quantum resource states in noisy environments using a quantum neural network

Quantum information processing tasks require exotic quantum states as a prerequisite. They are usually prepared with many different methods tailored to the specific resource state. Here we provide a versatile unified state preparation scheme based on a driven quantum network composed of randomly-coupled fermionic nodes. The output of such a system is then superposed with the help of linear mixing where weights and phases are trained in order to obtain desired output quantum states. We explicitly show that our method is robust and can be utilized to create almost perfect maximally entangled, NOON, W, cluster, and discorded states. Furthermore, the treatment includes energy decay in the system as well as dephasing and depolarization. Under these noisy conditions we show that the target states are achieved with high fidelity by tuning controllable parameters and providing sufficient strength to the driving of the quantum network. Finally, in very noisy systems, where noise is comparable to the driving strength, we show how to concentrate entanglement by mixing more states in a larger network.

quant-ph↗

arXiv2020

Distribution of quantum entanglement: Principles and applications

Quantum entanglement is a form of correlation between quantum particles that has now become a crucial part in quantum information and communication science. For example, it has been shown to enable or enhance quantum processing tasks such as quantum cryptography, quantum teleportation, and quantum computing. However, quantum entanglement is prone to decoherence as a result of interactions with environmental scatterers, making it an expensive resource. Therefore, it is crucial to understand its creation. We centre our attention to a situation where one would like to distribute quantum entanglement between principal particles that are apart. In this case, it is necessary to use ancillary systems that are communicated between them or interact with them continuously. Cubitt et al. showed that the ancillary systems need not be entangled with the principal particles in order to distribute entanglement. This has been demonstrated experimentally in the case of communicated ancillary particles and it is now known that the bound on the distributed entanglement is given by a communicated quantum discord. On the other hand, little is understood about the setting with continuous interactions, despite its abundant occurrence in nature. The main focus of this thesis is to study the distribution of quantum entanglement via continuous interactions with ancillary particles, which I will call mediators. I will present my work regarding the necessary conditions for entanglement distribution, the factors that are relevant for the distributed amount, and the speed limit to achieving maximum entanglement gain. Finally, I present some notable applications that can benefit from our work. This includes, among others, indirect probing of the quantum nature of optomechanical mirrors, photosynthetic organisms, and gravitational interactions.

quant-ph↗

arXiv2020

Observable quantum entanglement due to gravity

No experiment to date has provided evidence for quantum features of the gravitational interaction. Recently proposed tests suggest looking for the generation of quantum entanglement between massive objects as a possible route towards the observation of such features. Motivated by advances in optical cooling of mirrors, here we provide a systematic study of entanglement between two masses that are coupled gravitationally. We first consider the masses trapped at all times in harmonic potentials (optomechanics) and then the masses released from the traps. This leads to the estimate of the experimental parameters required for the observation of gravitationally induced entanglement. The optomechanical setup demands LIGO-like mirrors and squeezing or long coherence times, but the released masses can be light and accumulate detectable entanglement in a timescale shorter than their coherence times. No macroscopic quantum superposition develops during the evolution. We discuss the implications from such thought experiments regarding the nature of the gravitational coupling.

quant-ph↗

arXiv2018

Probing quantum features of photosynthetic organisms

Recent experiments have demonstrated strong coupling between living bacteria and light. Here we propose a scheme capable of revealing non-classical features of the bacteria (quantum discord of light-bacteria correlations) without exact modelling of the organisms and their interactions with external world. The scheme puts the bacteria in a role of mediators of quantum entanglement between otherwise non-interacting probing light modes. We then propose a plausible model of this experiment, using recently achieved parameters, demonstrating the feasibility of the scheme. Within this model we find that the steady state entanglement between the probes, which does not depend on the initial conditions, is accompanied by entanglement between the probes and bacteria, and provides independent evidence of the strong coupling between them.

quant-ph↗

arXiv2018

Detecting non-decomposability of time evolution via extreme gain of correlations

Non-commutativity is one of the most elementary non-classical features of quantum observables. Here we propose a method to detect non-commutativity of interaction Hamiltonians of two probe objects coupled via a mediator. If these objects are open to their local environments, our method reveals non-decomposability of temporal evolution into a sequence of interactions between each probe and the mediator. The Hamiltonians or Lindblad operators can remain unknown throughout the assessment, we only require knowledge of the dimension of the mediator. Furthermore, no operations on the mediator are necessary. Technically, under the assumption of decomposable evolution, we derive upper bounds on correlations between the probes and then demonstrate that these bounds can be violated with correlation dynamics generated by non-commuting Hamiltonians, e.g., Jaynes-Cummings coupling. An intuitive explanation is provided in terms of multiple exchanges of a virtual particle which lead to the excessive accumulation of correlations. A plethora of correlation quantifiers are helpful in our method, e.g., quantum entanglement, discord, mutual information, and even classical correlation. Finally, we discuss exemplary applications of the method in quantum information: the distribution of correlations and witnessing dimension of an object.

quant-ph↗

arXiv2017

Revealing non-classicality of inaccessible objects

Some physical objects are hardly accessible to direct experimentation. It is then desirable to infer their properties based solely on the interactions they have with systems over which we have control. In this spirit, here we introduce schemes for assessing the non-classicality of the inaccessible objects as characterised by quantum discord. We consider two probes individually interacting with the inaccessible object, but not with each other. The schemes are based on monitoring entanglement dynamics between the probes. Our method is robust and experimentally friendly as it allows the probes and the object to be open systems, makes no assumptions about the initial state, dimensionality of involved Hilbert spaces and details of the probe-object Hamiltonian. We apply our scheme to a membrane-in-the-middle optomechanical system, to detect system-environment correlations in open system dynamics as well as non-classicality of the environment, and we foresee potential benefits for the inference of the non-classical nature of gravity.

quant-ph↗

arXiv2015

Excessive distribution of quantum entanglement

We classify protocols of entanglement distribution as excessive and non-excessive ones. In a non-excessive protocol, the gain of entanglement is bounded by the amount of entanglement being communicated between the remote parties, while excessive protocols violate such bound. We first present examples of excessive protocols that achieve a significant entanglement gain. Next we consider their use in noisy scenarios, showing that they improve entanglement achieved in other ways and for some situations excessive distribution is the only possibility of gaining entanglement.

quant-ph↗