Quantum at Scale

Unifying quantum and classical physics has proved difficult as their postulates are conflicting. Using the notion of counts of the fundamental measures—length, mass, and time—a unifying description is resolved. A theoretical framework is presented in a set of postulates by which a conversion between expressions from quantum and classical physics can be made. Conversions of well-known expressions from different areas of physics (quantum physics, gravitation, optics and cosmology) exemplify the approach and mathematical procedures. The postulated integer counts of fundamental measures change our understanding of length, suggesting that our current understanding of reality is distorted.

As children, whispering into the ear of a friend in the presence of others allows us to pass a secret without interception, and forms one of the simplest attempts at secret communications we can employ. However, sending secret messages becomes deeply nontrivial over long distances. A solution for two parties to communicate securely is to encrypt and decrypt a message with two identical strings of bits, one for each party. In this case, the security of the encrypted message is provable and does not rely on assumptions on computational power. Quantum theory provides a clear solution for the initial distribution of these identical bit strings through Quantum Key Distribution. However, once long distances are involved, the corresponding loss involved in direct transmission ruins the effectiveness of quantum key distribution by reducing the effective rate exponentially with the distance. To circumvent the losses involved in direct transmission, quantum repeater architectures have been proposed. We present our contributions towards three aspects of quantum repeater systems in this thesis. We ensure conditions for implementing quantum repeaters with atomic ensembles, explore the option of optomechanical systems for implementing quantum repeaters and verify the success of completed quantum repeater protocols. In the first part of this thesis, we show how we can ensure conditions for the successful implementation of quantum repeater systems with atomic ensembles. These quantum repeater systems are formed with 1-dimensional networks, where the nodes are made up of quantum memories connected by means of single photons. This requires memories that are highly efficient. Also, if quantum repeater systems are implemented with hybrid resources, tunable photon waveforms will be desirable. We propose a protocol to implement quantum memories with atomic ensembles using a clear recipe to optimise the efficiency. We also demonstrate that a cold ensemble of Rubidium-87 can act as an efficient tunable source of single photons, along with flexibility in the produced temporal shapes. Next, we show how we can explore alternative options for the nodes of quantum repeater systems. We focus on optomechanical oscillators, and recognise that they can also be used as quantum memories. We present a witness to certify that this memory successfully operates in the quantum regime. Finally, we focus on the verification of successfully implemented quantum repeater protocols. This verification will be essential for certifying that quantum repeater systems operate as instructed. We use only local homodyne measurements to witness the success of the network, and find that the witness is robust to loss. We thus present distinct contributions towards three important aspects of quantum repeater systems. As far as a full-fledged quantum repeater system might seem to be right now, we have faith that our work brings the field of quantum-enabled secure communications forward.

Quantum networks are composed of quantum nodes which coherently interact by way of quantum channels. They offer powerful capabilities for quantum computation, communication, and metrology. A generic requirement for these realizations is the capability to generate and store quantum states among multiple quantum nodes, and to disseminate these resources throughout the network via the quantum channels. In this thesis, I describe a series of experiments whereby single excitations in atomic ensembles are strongly coupled to optical modes and provide efficient means for the coherent control of entangled states between matter and light. By following the seminal proposal by Duan et al., we have generated measurement-induced entanglement of an excitation between two cold atomic ensembles. Using this system, we investigated the relationship for the global bipartite entanglement and local correlations in its subsystems. In addition, we achieved functional quantum nodes for entanglement distribution. Two pairs of remote ensembles at two quantum nodes were prepared into entangled states in a heralded and asynchronous fashion by the conditional controls of the entanglement. The quantum states of the ensembles were then distributed into polarization entangled states of photons. We also prepared an analogous quantum state and transferred the nonlocal coherence between two pairs of heralded entangled atomic ensembles, providing a step towards entanglement connection. Beyond such probabilistic approaches, we demonstrated an experiment where entanglement between two quantum memories is created by the reversible and deterministic mapping of an entangled state of light via dynamic electromagnetically induced transparency. This experiment opens novel prospects of integrating hybrid quantum systems by way of reversible quantum interfaces between light and matter. Then, we extended our work to multipartite quantum systems. We theoretically investigated the characterization of multipartite mode-entangled states by way of quantum uncertainty relations, and introduced theoretical tools to verify the entanglement orders in multipartite systems. In particular, we achieved entanglement for one delocalized photon among multiple optical modes (N > 2). Finally, we have achieved measurement-induced entanglement of spin waves among four quantum memories. The individual atomic components for the entangled W state of the four ensembles were then coherently converted into four propagating entangled beams of light via superradiant emissions. We observed the statistical and dynamic transitions for the multipartite entangled spin waves. Experiments described in this thesis thereby represent significant advances of experimental and theoretical capabilities to generate, store, transfer, and characterize entanglement of matter and light over quantum networks.

Matter-wave dualism is a fundamental concept in quantum physics. The observation of wave properties of heavy organic molecules can be used to approach the borderline between classical and quantum physics. Up to which mass and size do particles or molecules still have wave properties? This question is subject to be answered within this thesis and as part of the international nanoquestfit-project where many researchers of different disciplines are involved.
\nThis thesis is a summary of the work done within a research collaboration between the group of Prof. Dr. Marcel Mayor (University of Basel) and the group of Prof. Dr. Markus Arndt (University of Vienna). The work is mainly focused on the development of novel quantum interference experiments that imply the development of new synthetic strategies towards tailor-made molecules. Novel interferometers have been developed by the Arndt group and therefore the molecular requirements changed strongly within the past years. The syntheses of these tailor-made molecules were performed by the author in the laboratories of Prof. Mayor in Basel. Quantum interference experiments and the preliminary investigations described within this work, namely the thermal stability test, the desorption studies and the laser-induced acoustic desorption have been performed by the Arndt group in Vienna.
\nInvestigations at the interface of quantum and classical physics are a fascinating part of the research. The final goal is to approach the quantum-to-classical transition by the observation of quantum properties of large and complex molecules. In order to study the wave nature of such particles—a purely quantum mechanical phenomenon—synthetic procedures towards tailor-made compounds are developed to improve the observation of this phenomenon through matter-wave experiments. 
\nAt the starting point of this work, a series of highly fluorinated porphyrin-monomers set a new benchmark in high-mass quantum interference experiments. The highest masses of particles used in quantum interference experiments were around 10’000 g/mol. Thus, our objective was to reach masses up to 25’000 g/mol with the suitable features for the quantum interferometry experiments.
\nIn the first chapter of this thesis, the principle of interferometry, the development and evolution of this technology are presented. In the subsequent chapters, the different synthetic approaches of the tailor-made molecules designed to improve the measurements and achieve the goal of this thesis are described.
\nThe main part of this thesis is focused on the synthesis of tailor-made molecules for quantum interference experiments. In a first part, the synthesis of a novel, more massive fluorinated phthalocyanine is presented. That phthalocyanine was used in far-field quantum interference experiments. Unfortunately, the molecular requirements could not been tuned to observe wave-particle duality in these experiments. The second part focuses on the synthesis of three different molecular libraries. Molecular libraries are mixtures of molecules having the same core but a to some extent random number of long perfluorinated chains. The individual members within the library were observable in MALDI-TOF mass spectrometry. We attached the chains to three different cores to obtain three different molecular libraries. To produce a first generation of libraries we used diacetylene bond porphyrin-dimer. The rather limited reaction scope of diacetylene bond porphyrins was enhanced by the second generation of tetramers and pentamers. To compare the modularity of the synthesis of oligo-porphyrin systems two additional cores, a porphyrin-dimer and a porphyrin-trimer, have also been synthesized. The possibility to produce a molecular beam with the three molecular-libraries has been investigated by thermal studies, desorption experiments and laser-induced acoustic desorption.
\nThe last part of the thesis is focused on the synthesis of photocleavable tags that can be attached to model compounds. These tags are synthesized since novel quantum interference experiments are based on light gratings where a mass difference is supposed to be observed at the detector level upon cleavage. The final idea is, in the near future, to attach these molecules to large particles, such as metal-nanoparticles, clusters or proteins. It is expected to enable the detection of mass differences of the intact clusters and the clusters with the cleaved tags. Three different model compounds have been synthesized. The cleavage of the tags was proven in solution upon irradiation of UV-light in solution, where a constant and reproducible decay was observed. In future quantum interference experiments, the cleavage should be performed in gas-phase as a final prove of concept. The molecules are currently under investigations in the Arndt group.

"Application-driven quantum and statistical physics: a short course for future scientists and engineers, volume 2: equilibrium." Contemporary Physics, 61(3), pp. 220–221

Semiconductor quantum dots are usually compared to artificial atoms, because their electronic structure consists of discrete energy levels as for natural atoms. These artificial systems are integrated in solid materials and can be localized with a spatial precision of the order of nanometers. Besides, they conserve their quantum properties even at quite high temperatures (∼ 10 K). These properties make quantum dots one of the most suitable systems for the realization of quantum devices and computers. However, the energy states and the optical properties of quantum dots are much more complicated than for atoms, because a quantum dot is never an isolated potential well. Instead, its electronic structure depends on the crystallin structure of the semiconductor material and on the Coulomb ion-electron and electron-electron correlations. In particular, the presence of several valence bands and their mixing, induced by quantum confinement, gives rise to novel properties which are still not completely understood and exploited in applications. To get a major advance in this field, a full deterministic control of the spatial shape of the quantum confinement is needed, combined with a deeper understanding of the connections between electronic and optical properties. This thesis work has these two main objectives. We realized and experimentally studied different quantum dot systems, in pyramidal hetero-structures grown with MOCVD techniques. These systems allowed the realization of several different geometries for the carrier confining potential, with a precision in the order of nanometers. The optical characterization has been obtained in particular by means of polarization-resolved microphotoluminescence, magneto-photoluminescence, excitation photoluminescence (PLE), and interferometry techniques. For single quantum dots, we have observed and characterized for the first time new excitonic complexes, arising from excited hole states. This allowed a full caracterizatioon of the valence band hole states in our peculiar system. By means of photon correlation measurements, we have also experimentally demonstrated that, even in presence of a large family of exciton states, these quantum dot systems can emit single photons. We have then realized much more complex quantum dot structures, double dot systems (quantum dot molecules) and a completely new system called Dot-in-Dot (DiD). This latter is composed by a small inner dot surrounded by an electrostatic potential well (which can be considered as an outer elongated dot). Such a composite system is characterized by a strong valence band mixing. This state superposition is however very sensitive to small variations of the confining potential. Therefore the degree of valence band mixing can be easily switched by the introduction of a week external field. Since the valence band mixing determines the polarization properties of the emitted light, the DiD changes the polarization properties of its emission spectrum under the action of an external field. In particular, we have experimentally demonstrated this effect for an external static magnetic field, while we have numerically predicted a very similar effect for a static electric field. In the latter case, the polarization switching is a direct consequence of the quantum confined Stark effect induced in the DiD. Hence the DiD appears to be an ideal candidate for realizing emitters of single photons with tunable and controllable polarization.

The goal of this work is to provide a positive result of quantum obfuscation. Point functions have been widely discussed in classical obfuscation theory but yet not formally defined in the quantum setting. To analyze the obfuscatability of quantum point functions, we start with preliminaries on quantum obfuscation, giving out the oracle-implementable relationship of two quantum circuit families and some obfuscations of combined quantum circuits. Then, we present the strict definition of a quantum point function and discuss its variants of multiple points and multiple qubits. Under the quantum-accessible random oracle model, we obtain the obfuscatability of quantum point function families by means of reduction. Finally, we discuss the application of quantum obfuscation in quantum zero-knowledge. As a start of study on quantum point functions, our work will be inspiring in the future development of quantum obfuscation theory.

The two dimensional electron gas subjected to a perpendicular magnetic field is a model system that supports a variety of electronic phases. Perhaps the most well-known are the fractional quantum Hall states, but in recent years there has been an upsurge of interest in the charge ordered phases commonly referred to as electron solids. These solids are a consequence of electron-electron interactions in a magnetic field. While some solid phases form in the lowest Landau level, the charged ordered phases are most abundant in the higher Landau levels. Examples of such phases include the Wigner solids, electronic bubble phases and stripe or nematic phases. Open questions surround the exact role of disorder, confinement potential, temperature and the Landau level index in determining the stability and competition of these phases with other ground states. The interface of GaAs/AlGaAs remains the cleanest host for the two-dimensional electron gas due to the extremely high quality of materials available and the advancement in molecular beam epitaxy growth techniques. As a result, exceptionally high electron mobilities in this system have been instrumental in the discovery of numerous electron solids. In this Thesis, I discuss the discovery and properties of several electron solids that develop in such state-of-the-art two dimensional electron gases. These electron solids often develop at ultra low temperatures, in the milliKelvin temperature range. After an introduction to the physics of the quantum Hall effect in two dimensions, in chapter 3, I discuss electron solids developing in the N=1 Landau level. While these solids have been known for some time, details of the competition of these phases xiii with the nearby fractional quantum Hall states remains elusive. A number of reports observe new fractional quantum Hall states at filling factors where electron solids are found in other experiments. We undertook a systematic study to answer some of these unsettled questions. We see evidence for incipient fractional quantum Hall states at 2+2/7 and 2+5/7 at intermediate temperatures which are overtaken by the electronic bubble phases at lower temperatures. Several missing fractional states including those at filling factors 2+3/5, 2+3/7, 2+4/9 highlight the relative stability of the electronic solids called the bubble phases in the vicinity in our sample. In chapter 4, I discuss a newly seen electron crystal which manifests itself in transport measurements as a reentrant integer quantum Hall state. Reentrant integer behavior is common in high Landau levels, but so far it was not observed in the lowest Landau level in narrow quantum well samples. In contrast to high Landau levels, where such reentrant integer behavior was associated with electronic bubbles, we believe that the same signature in the N=0 Landau level is due to an electronic Wigner crystal. The filling factors at which we observe such reentrance reveal that it is a crystal of holes, rather than electrons. The discovery of this reentrant integer state paints a complex picture of the interplay of the Wigner crystal and fractional quantum Hall states. Finally, in chapter 5, I discuss the observation of a novel phenomenon, that of reentrant fractional quantum Hall effect. In the lowest Landau level, we observe a fractional quantum Hall state, but as the field is increased, we see a deviation and then a return to quantization in the Hall resistance. Such a behavior indicates a novel electron solid. In contrast to the collective localization of electrons evidenced by the reentrant integer quantum Hall effect, such reentrance to a fractional Hall resistance clearly points to the involvement of composite fermion quasiparticles. This property thus distinguishes the ground state we observed as a solid formed of composite fermions. Such a solid phase is evidence for exotic electron-electron correlations at play which are clearly different from those in the traditional Wigner solid of electrons.

Since the first communication systems were developed, the scientific community has been witnessing attempts to increase the amount of information that can be transmitted. In the last 10--15 years there has been a tremendous amount of research towards developing multi-antenna systems which would hopefully provide high-data-rate transmissions. However, increasing the overall amount of transmitted information increases the complexity of the necessary signal processing. A large portion of this thesis deals with several important issues in signal processing of multi-antenna systems. In almost every particular case the goal is to develop a technique/algorithm so that the overall complexity of the signal processing is significantly decreased. In the first part of the thesis a very important problem of signal detection in MIMO (multiple-input multiple-output) systems is considered. The problem is analyzed in two different scenarios: when the transmission medium (channel) 1) is known and 2) is unknown at the receiver. The former case is often called coherent and the later non-coherent MIMO detection. Both cases usually amount to solving highly complex NP-hard combinatorial optimization problems. For the coherent case we develop a significant improvement of the traditional sphere decoder algorithm commonly used for this type of detection. An interesting connection between the new improved algorithm and the H-infinity estimation theory is established, and the performance improvement over the standard sphere decoder is demonstrated. For the non-coherent case we develop a counterpart to the standard sphere decoder, the so-called out-sphere decoder. The complexity of the algorithm is viewed as a random variable; its expected value is analyzed and shown to be significantly smaller than the one of the overall exhaustive search. In the non-coherent case, in addition to the complexity analysis of the exact out-sphere decoder, we analyze the performance loss of a suboptimal technique. We show that only a moderate loss of a few dbs in power required at the transmitter will occur if a polynomial algorithm based on the semi-definite relaxation is used in place of any exact technique (which of course is not known to be polynomial). In the second part of the thesis we consider a few problems that arise in wireless broadcast channels. Namely, we consider the problem of the information symbol vector design at the transmitter. A polynomial linear precoding technique is constructed. It enables achieving data rates very close to the ones achieved with DPC (dirty paper coding) technique. Additionally, for another suboptimal polynomial scheme (the so-called nulling and cancelling), we show that it asymptotically achieves the same data rate as the optimal, exponentially complex, DPC. In the last part of the thesis we consider a quantum counterpart of the signal detection from classical communication. In quantum systems the signals are quantum states and the quantum detection problem amounts to designing measurement operators which have to satisfy certain quantum mechanics laws. A specific type of quantum detection called unambiguous detection, which has numerous applications including quantum filtering, has recently attracted a lot of attention in the research community. We develop a general framework for numerically solving this problem using the tools from the convex optimization theory. Furthermore, in the special case where the two quantum states are of rank 2, we construct an explicit analytical solution for the measurement operators. At the end we would like to emphasize that the contribution of this thesis goes beyond the specific problems mentioned here. Most algorithmic optimization techniques developed in this paper are generally applicable. While it is a fact that our results were originally motivated by wireless and quantum communications applications, we believe that the developed techniques will find applications in many different areas where similar optimization problems appear.

Two-photon, three-photon, and four-photon near-infrared quantum cutting luminescence of Er3+: oxyfluoride vitroceramics are studied. X-ray diffraction, absorption, visible to near infrared luminescence and excitation spectra of Er3+-doped oxyfluoride vitroceramics have been measured. We found that when the concentration of the Er3+ ion increased from 0.5% to 2., the infrared excitation spectra intensities of the Er3+ ion enhanced by approximately 5.64, 4.26, 2.77, 7.31, 6.76, 4.75, 2.40, 11.14, 2. 88, and 4.61 times for the I-4(15/2)->(2)G(7/2), I-4(15/2)->(4)G(9/2), I-4(15/2)->(4)G(11/2), I-4(15/2)-> H-2(9/2), I-4(15/2)->(F-4(3/2), F-4(5/2)) I-4(15/2)-> F-4(7/2), I-4(15/2)-> H-2(11/2), I-4(15/2)-> S-4(3/2), I-4(15/2)-> F-4(9/2), and I-4(15/2)-> I-4(9/2) transitions. Meanwhile, it can also be found that the visible excitation spectra intensity of the Er3+ ion decreased by approximately 1. 36, 1.93, 3.43, 1.01, 2.24, and 2.28 times for the I-4(15/2)->(2)G(7/2), I-4(15/2)->(4)G(9/2), I-4(15/2)->(4)G(11/2), I-4(15/2)-> H-2(9/2), I-4(15/2)->(F-4(3/2), F-4(5/2)) and I-4(15/2)-> F-7/2 absorption transitions of the Er3+ ion, respectively. That is to say, the samples exhibited a 2 to 11 times enhancement in both infrared luminescence and excitation intensities, with a concomitant one to three times decreasing of both visible luminescence and excitation intensities. Moreover, the excitation spectra of 1 543. 0 and 550. 0 nm luminescence were very similar both in shape and peak wavelength, confirming that the multiphoton near-infrared quantum cutting luminescence phenomena were found. In order to analyze the process and mechanism of quantum cutting better, we measured the variation of main visible and infrared luminescence intensity based on the excitation intensity. It found that all visible and infrared luminescence intensity was linear depended on the excitation intensity basically. In which, the variation of the visible luminescence intensity depended on the excitation intensity was slightly larger than linear. It is resulted from the very small absorption of excited state. The variation of the infrared 1 543. 0 nm luminescence intensity depended on the excitation intensity was slightly smaller than linear. It is the characteristic phenomena of quantum cutting luminescence. It found that two-photon quantum cutting luminescence of I-4(9/2) state mainly resulted from the {I-4(9/2)-> I-4(13/2), I-4(15/2)-> I-4(13/2)} ETr31-ETa01 cross-energy transfer process. Three-photon quantum cutting luminescence of the S-4(3/2) state mainly result from the {S-4(3/2)-> I-4(9/2), I-4(15/2)-> I-4(13/2)} ETr31-ETa01 and {I-4(9/2)-> I-4(13/2), I-4(15/2)-> I-4(13/2)} ETr31-ETa01 cross-energy transfer process. Four-photon quantum cutting of H-2(9/2) mainly results from the {H-2(9/2)-> I-4(13/2), I-4(15/2), S-4(3/2)}ETr91-ETa05 {S-4(3/2)-> I-4(9/2), I-4(15/2)-> I-4(13/2)} ETr53-ETa05 and {I-4(9/2)-> I-4(13/2), I-4(15/2)-> I-4(13/2)} ETr31-ETa01 cross-energy transfer process. These measured results are useful for the next-generation of quantum cutting solar cells, a current hot point globally.

Traditional electronic and communication devices operate by processing binary information encoded as bits. Such digital devices have led to the most advanced technologies that we encounter in our everyday lives and they influence virtually every aspect of our society. Nonetheless, there exists a much richer way to encode and process information. By encoding information in quantum mechanical states as qubits, phenomena such as coherence and entanglement can be harnessed to execute tasks that are intractable to digital devices. Under this paradigm, it should be possible to realize quantum computers, quantum communication networks and quantum sensors that outperform their classical counterparts. The electronic spin states of color-center defects in the semiconductor silicon carbide have recently emerged as promising qubit candidates. They have long-lived quantum coherence up to room temperature, they can be controlled with mature magnetic resonance techniques, and they have a built-in optical interface operating near the telecommunication bands. In this thesis I will present two of our contributions to this field. The first is the electric-field control of electron spin qubits. This development lays foundation for quantum electronics that operate via electrical gating, much like traditional electronics. The second is the universal control and entanglement of electron and nuclear spin qubits in an ensemble under ambient conditions. This development lays foundation for quantum devices that have a built-in redundancy and can operate in real-world conditions. Both developments represent important steps towards practical quantum devices in an electronic grade material.

<span lang="EN-US">With the growing revolution in the education system, imparting quality education has become a priority for instructors and students in any educational institution. The challenge grows high when it comes to teaching advanced subjects like quantum physics. The present study considered the case study of the University of Rwanda College of Education. It investigated the impact of current teaching methodologies and teaching staff and students’ perceptions in quantum physics for a quality knowledge delivery system. It employed a quantitative method of data collection. About 300 students and ten lecturers participated in this study. Data obtained from this study were analyzed using descriptive quantitative analysis. Students suggested that multimedia tools in teaching and learning quantum physics can improve the understanding of concepts and help solve complex mathematical problems in quantum physics. Likewise, the teaching staff finds quantum physics more comprehensive and effective when appropriate multimedia tools are used. The investigation outcome is meant multimedia utilization can improve quantum physics’ teaching and learning experience at Rwanda high educational institutions.</span>

An approach to quantum physics (QP) is proposed that is characterized by the attempt to give up the verificationist theory of truth underlying the standard interpretation of QP. As a first step, anobservatively minimal language L is constructed that is endowed with a Tarskian truth theory. Then, a set of axioms is stated by means of L that hold both in classical physics and in QP, and the further language Le of all properties is constructed. The concepts ofmeaning andtestability do not collapse in L and Le, hence quantum logic is interpreted as a theory of testability in QP, and QP turns out to be semantically incomplete. Furthermore, semantic and pragmatic compatibility of physical properties are distinguished in Le, and the concepts of testability and conjoint testability of statements are introduced. In this context some known quantum paradoxes can be avoided, and a new general principle (MGP) characterizes the truth mode of empirical physical laws. MGP invalidates the Bell theorem and, presumably, the Bell-Kochen-Specker theorem, and introduces apragmatic contextuality in QP in place of thesemantic contextuality that should occur because of these theorems.

Effective instructional strategies have been highlighted in teaching Quantum physics (QP) since this topic is theoretically complex and different from classical physics. In addressing this issue, a needs analysis (NA) was carried out to identify the anticipated challenges in QP learning and facilitation (L&F) and the integration of STEM education in a physics classroom. This research is a qualitative study where a semi-structured interview was conducted with two experts in physics education and two physics teachers selected under a purposive sampling approach. The interview was one-on-one through online platforms, held during the Covid-19 pandemic’s mobility control order (MCO). The data from the semi-structured interview was analysed using thematic analysis, and the findings were presented as thematic maps. Two major themes emerged from the thematic analysis: 1) the expectation in QP L&F based on experts’ and teachers’ views and 2) the discrepancies in SSQP-STEM L&F gathered from the teachers’ opinions and perspectives. The first theme denotes 1.1) teachers’ professional development, 1.2) pedagogical content knowledge, 1.3) instructional strategy, and 1.4) QP L&F resources. The second theme describes the discrepancies of SSQP-STEM L&F in terms of 2.1) QP nature, 2.2) insufficiency of resources in QP L&F, and 2.3) teachers’ perceptions of students’ characteristics in the physics classroom, and 2.4) the teachers’ competencies issues in teaching QP. Overall, the finding shows that a practical instructional module needs to be developed to cater to the physics teachers' demands.

In quantum information science, photons are the best candidate for transmitting information, and atoms are the best candidate for storing information. The combination of these two systems provides a fascinating future for practical applications of the quantum information concepts. The work presented in this thesis mainly consists of two parts. The first part is about manipulation of entangled photons, including the demonstration of a nondestructive CNOT gate, the creation of narrowband entangled photons through cavity-enhanced spontaneous parametric down-conversion, and the realization of interference between narrowband photon sources. The second part is about manipulation of atomic ensembles. The main purpose for this part is to extend the quantum communication distance using the concept of quantum repeater. Within this part, the experimental work includes, the extension of storage lifetime of quantum memories to 1 ms by increasing the wavelength of stored spinwave, the realization of entanglement assisted spinwave interferometer, the demonstration of efficient entanglement swapping with quantum memories, and the realization of quantum teleportation between atomic ensembles.