Over the past three decades, quantum mechanics has allowed the development of technologies that provide unconditionally secure communication. In parallel, the quantum nature of the transverse electromagnetic field has spawned the field of quantum imaging that encompasses technologies such as quantum ghost imaging and high-dimensional quantum key distribution (QKD). The emergence of such quantum technologies also highlights the need for the development of methods for characterizing the elusive quantum state itself. In this document, we describe new technologies that use the quantum properties of light for security. The first is a technique that extends the principles behind QKD to the field of imaging. By applying the polarization-based BB84 protocol to individual photons in an active imaging system, we obtained images that are secure against intercept-resend jamming attacks. The second technology presented in this article is based on an extension of quantum ghost imaging. We used a holographic filtering technique to build a quantum ghost image identification system that uses a few pairs of photons to identify an object from a set of known objects. The third technology addressed in this document is a high-dimensional QKD system that uses orbital-angular-momentum (OAM) modes of light for encoding. Moving to a high-dimensional state space in QKD allows one to impress more information on each photon, as well as introduce higher levels of security. We discuss the development of two OAM-QKD protocols based on the BB84 and Ekert QKD protocols. The fourth and final technology presented in this article is a relatively new technique called direct measurement that uses sequential weak and strong measurements to characterize a quantum state. We use this technique to characterize the quantum state of a photon with a dimensionality of d=27, and measure its rotation in the natural basis of OAM.
Over the past three decades, quantum mechanics has allowed the development of technologies that provide unconditionally secure communication. In parallel, the quantum nature of the transverse electromagnetic field has spawned the field of quantum imaging that encompasses technologies such as quantum ghost imaging and high-dimensional quantum key distribution (QKD). The emergence of such quantum technologies also highlights the need for the development of methods for characterizing the elusive quantum state itself. In this document, we describe new technologies that use the quantum properties of light for security. The first is a technique that extends the principles behind QKD to the field of imaging. By applying the polarization-based BB84 protocol to individual photons in an active imaging system, we obtained images that are secure against intercept-resend jamming attacks. The second technology presented in this article is based on an extension of quantum ghost imaging. We used a holographic filtering technique to build a quantum ghost image identification system that uses a few pairs of photons to identify an object from a set of known objects. The third technology addressed in this document is a high-dimensional QKD system that uses orbital-angular-momentum (OAM) modes of light for encoding. Moving to a high-dimensional state space in QKD allows one to impress more information on each photon, as well as introduce higher levels of security. We discuss the development of two OAM-QKD protocols based on the BB84 and Ekert QKD protocols. The fourth and final technology presented in this article is a relatively new technique called direct measurement that uses sequential weak and strong measurements to characterize a quantum state. We use this technique to characterize the quantum state of a photon with a dimensionality of d=27, and measure its rotation in the natural basis of OAM.
This presentation first reviews the historical development of the field of nonlinear optics, starting from its inception in 1961. It then reviews some of its more recent developments, including especially how nonlinear optics has become a crucial tool for the developing field of quantum technologies. Fundamental quantum processes enabled by nonlinear optics, such as the creation of squeezed and entangled light states, are reviewed. We then illustrate these concepts by means of specific applications, such as the development of secure communication systems based on the quantum states of light. We are also interested in studying the properties of structured light fields. These structured light beams have recently been shown to possess exotic properties of their own, such as vacuum propagation velocities differing from the light velocity c for plane waves. These beams can also be tailored in such a way that they carry orbital angular momentum, which can be used to apply a torque to mechanical objects and as a carrier of information in a classical and quantum telecommunication system. Light can carry angular momentum both by means of its spin angular momentum (as manifested for example in circular polarization) and by means of its orbital angular momentum (OAM), whose origin is a helical structure of its wavefront. The orbital angular momentum of light has recently been recognized to constitute a crucial attribute for many photonic technologies, including the trapping and manipulation of small particles and for multiplexing in optical telecommunication. In this presentation we review some of the fundamental properties of OAM including its quantum features such as entanglement. We then go on to describe a secure telecommunication system in which information is encoded in OAM, and which can carry more than one bit of information per photon.
In this thesis, Quantum Key Distribution and quantum communication methods based on high-dimensional spatial coding of light are developed. Their security is based on the fundamental quantum nature of light and profits from the highdimensional Hilbert spaces offered intrinsically by imaging optics. An overview of classical information theory and quantum information is given to introduce the field of quantum cryptography. The advantages of larger dimensional alphabets and the security of the standard two-bases BB84 protocol is shown. The spatial states used for encoding are introduced. An analytic expression for the upper bound on the mutual information for these states is derived, including multiphoton states, detector noise and beam broadening. High-dimensional encoding of single photons is experimentally realized, reaching 10.5 bit per received photon. The dependence of the mutual information on the number of detector pixels is discussed and the experimental values are compared with the theoretical upper bound. It was shown that a standard error-correcting LDPC code is sufficient to achieve practically error-free communication. By adding a second mutually unbiased basis, a large-alphabet QKD system is experimentally realized and characterized. The security of this BB84-like protocol is analyzed in terms of intercept-resend and collective attacks. The key rate after postprocessing is analyzed under realistic circumstances, including finite key length. Finally, a new quantum communication method is demonstrated, which is based on encoding information into wavefronts decomposed over guided modes of a multimode fiber. At the end a step back is made and the similarities and differences of several quantum authentication and quantum cryptography schemes as well as Quantum Data Locking are discussed. This involves comparison of the characteristics of the classical channel, the quantum channel and the necessary dimension of the Hilbert space.
We present a quantum secure imaging (QSI) scheme based on the phase encoding and weak+vacuum decoy-state BB84 protocol of quantum key distribution (QKD). It allows us to implement a computational ghost imaging (CGI) system with more simplified equipment and reconstructed algorithm by using a digital micro-mirror device (DMD) to preset the specific spatial distribution of the light intensity. What is more, the quantum bit error rate (QBER) and the secure key rate analytical functions of QKD are used to see through the intercept-resend jamming attacks and ensure the authenticity of the imaging information. In the experiment, we obtained the image of the object quickly and efficiently by measuring the signal photon counts with a single-photon detector (SPD), and achieved a secure key rate of 571.0 bps and a secure QBER of 3.99%, which is well below the lower bound of QBER of 14.51%. Besides, our imaging system uses a laser with invisible wavelength of 1550 nm, whose intensity is as low as single-photon, that can realize weak-light imaging and is immune to the stray light or air turbulence, thus it will become a better choice for quantum security radar against intercept-resend jamming attacks.
Abstract Cryptography plays an important role in information security, which is widely applied in the various fields of society. Quantum cryptography has shown its great advantages in information security compared with the classical one. Two major directions of quantum cryptography are quantum key distribution (QKD) and quantum encryption, with the former focusing on secure key distribution and the latter focusing on encryption using quantum algorithms. In contrast to the well accepted success of the QKD, the development of quantum encryption is rather limited because of the difficulties of building up algorithms and the constructing the practical quantum computers. Here we propose a new scheme of quantum encryption based on high-dimensional entanglement holography. Firstly, we experimentally realize the quantum holography based on the high-dimensional orbital angular momentum (OAM) entanglement. Then, OAM-selective holographic scheme for quantum encryption is proposed and demonstrated. Our results show that introducing quantum entangled state into OAM holography makes the OAM holography possess infinite information channels and the transmission of information be absolute security in principle. Furthermore, decryption in the presence of strong noise is achieved. Our work opens up a new way to realize quantum information security.
Quantum information processing (QIP) is an interdisciplinary field concerned with the development of computers and information processing systems that utilize quantum mechanical properties of nature to carry out their function. QIP systems have become vastly more practical since the turn of the century. Today, QIP applications span imaging, cryptographic security, computation, and simulation (quantum systems that mimic other quantum systems). \nMany important strategies improve quantum versions of classical information system hardware, such as single photon detectors and quantum repeaters. Another more abstract strategy engineers high-dimensional quantum state spaces, so that each successful event carries more information than traditional two-level systems allow. Photonic states in particular bring the added advantages of weak environmental coupling and data transmission near the speed of light, allowing for simpler control and lower system design complexity. \n \nIn this dissertation, numerous novel, scalable designs for practical high-dimensional linear-optical QIP systems are presented. First, a correlated photon imaging scheme using orbital angular momentum (OAM) states to detect rotational symmetries in objects using measurements, as well as building images out of those interactions is reported. Then, a statistical detection method using chains of OAM superpositions distributed according to the Fibonacci sequence is established and expanded upon. It is shown that the approach gives rise to schemes for sorting, detecting, and generating the recursively defined high-dimensional states on which some quantum cryptographic protocols depend. \n \nFinally, an ongoing study based on a generalization of the standard optical multiport for applications in quantum computation and simulation is reported upon. The architecture allows photons to reverse momentum inside the device. This in turn enables realistic implementation of controllable linear-optical scattering vertices for carrying out quantum walks on arbitrary graph structures, a powerful tool for any quantum computer. It is shown that the novel architecture provides new, efficient capabilities for the optical quantum simulation of Hamiltonians and topologically protected states. Further, these simulations use exponentially fewer resources than feedforward techniques, scale linearly to higher-dimensional systems, and use only linear optics, thus offering a concrete experimentally achievable implementation of graphical models of discrete-time quantum systems.
We have built an imaging system that uses a photon's position or time-of-flight information to image an object, while using the photon's polarization for security. This ability allows us to obtain an image which is secure against an attack in which the object being imaged intercepts and resends the imaging photons with modified information. Popularly known as “jamming,” this type of attack is commonly directed at active imaging systems such as radar. In order to jam our imaging system, the object must disturb the delicate quantum state of the imaging photons, thus introducing statistical errors that reveal its activity.