Biometric identification for forensic investigations and security continues to depend on classic fingerprinting in many
instances. Existing techniques rely on either visible deposits or hidden (latent) fingerprints resulting from the transfer of
residues from the finger to the surface. However, one of the limitations of classic fingerprinting, for use as forensic
evidence, is in determining a time sequence of events. It is extremely difficult to establish a timeline, from fingerprint
evidence alone. We present the capability of a new technique which images the electrical charge deposited by
tribocharging when a finger contacts an electrically insulated surface. The method is applicable to insulating surfaces and
has been tested on PVC, PTFE, Acetate and PVDF sheets. The latent electrostatic charge pattern is detected using a
novel, microscopic, electric potential sensor. The sensor is capable of imaging static charge distributions non-invasively,
with no discharging effect on the sample. We present data showing the decay of the charge image with time, over a
period up to 14 days. This capability has two major implications. First this technique does not suffer from ambiguities
caused by a history of old fingerprints and second it has the potential to allow the time sequence of recent charge
fingerprint images to be determined.
We have reported previously on the use of a novel Electric Potential Sensor, developed and patented at the University of
Sussex, for remote monitoring of life signs and through-wall sensing of movement and proximity. In this paper we
present the data obtained using a sparse (4-element) array of sensors to image a volume of space for target movements.
This is achieved by passive monitoring of the disturbances which result from the movement of a dielectric object through
the ambient electric field. Numerical computation is used to simulate the expected sensor responses for a given pattern of
movement and comparison with these simulations allows the trajectory to be followed. With this 4-element array, it is
possible to track the movement of a single subject, for example an intruder, or the lone occupant of a room. However,
with the addition of just a few extra sensors, it is possible to resolve the ambiguities caused by multiple targets. The
advantage of this approach over competing technologies such as radar, for through-wall surveillance and tracking, is that
the method is passive. It requires no excitation field or probe signal and relies instead on the ambient static electric field
which exists between the ionosphere and the surface of the Earth. It therefore only works well if the array is not
obstructed by earthed conducting materials, in common with the other technologies. On the other hand, the passive
nature of the technique provides a low power system which is potentially undetectable.
In this paper we outline the application of a novel electric field sensor technology, developed and patented at the
University of Sussex, to the sensing of movement and proximity, using a technique which is generally unaffected by the
presence of walls and other structures. This is achieved by monitoring electric field disturbances which occur when a
large dielectric object, such as a human or animal body, is moved through the ambient electric field. These sensors
detect, passively, changes in spatial potential (electric field) created by a capacitively coupled electric field. To date we
have already demonstrated the potential applications of these devices, in principle, across many areas of interest,
including body electrophysiology, novel nuclear magnetic resonance (NMR) probes, non destructive testing of
composite materials as well as the detection of a heart beat from distances of up to 40 cm. Here we show how, with
multiple sensors in a variety of spatial arrangements, it is possible to use simple signal processing and analysis in
Labview to detect movement, give an indication of direction and speed as well as track position within an open
A new generation of electric field sensors developed at the University of Sussex is enabling an alternative to contact
voltage and non-contact magnetic field measurements. We have demonstrated the capability of this technology in a
number of areas including ECG through clothing, remote off-body ECG, through wall movement sensing and electric
field imaging. Clearly, there are many applications for a generic sensor technology with this capability, including long
term vital sign monitoring. The non-invasive nature of the measurement also makes these sensors ideal for man/machine
and human/robot interfacing. In addition, there are obvious security and biometric possibilities since we can obtain
physiological data remotely, without the knowledge of the subject. This is a clear advantage if such systems are to be
used for evaluating the psychological state of a subject. In this paper we report the results obtained with a new version of
the sensor which is capable of acquiring electrophysiological signals remotely in an open unshielded laboratory. We
believe that this technology opens up a new area of remote biometrics which could have considerable implications for
security applications. We have also demonstrated the ability of EPS to function in closely-packed one and two
dimensional arrays for real-time imaging.
There are a number of systems that are currently being considered as candidates for the construction of qubits, quantum logic gates and quantum computers. Some of the systems, notably atoms in magnetic traps and nuclear magnetic resonance (NMR) systems, have had some success in performing the elementary operations that would be required in large-scale quantum computer. However, these systems are not necessarily seen as viable technologies for quantum computing in the longer term. The recent demonstration of macroscopic coherence in a superconducting ring (consisting of a thick superconducting ring containing one or more Josephson weak link devices) has added significant weight to the idea of using superconducting persistent current devices (SQUIDs) in quantum logic systems. In this paper, we consider one aspect of the quantum mechanical SQUID, the nonlinear effect of SQUID on the classical control parameters, and we discuss how it may influence the construction and design of quantum logic gates based on SQUID devices. In particular, we look at problems associated with fixing the classical magnetic flux bias for a quantum mechanical SQUID at, or near, a quantum mechanical transition or resonance.
This paper considers the behavior of a model persistent current qubit in the presence of a time-dependent electromagnetic field. A semi-classical approximation for the electromagnetic field is used to solve the time- dependent Schrodinger equation (TDSE) for the qubit, which is treated as a macroscopic quantum object. The qubit is describe3d by a Hamiltonian involving the enclosed magnetic flux (Phi) and the electric displacement flux Q, which obey the quantum mechanical commutation relation. The paper includes a brief summary of recent work on quantum mechanical coherence in persistent current circuits, and the solution of the TDSE in superconducting rings. Of particular interest is the emergence of strongly non-perturbative behavior that corresponds to transitions between the energy levels of the qubit. These transitions are due to the strong coupling between the electromagnetic fields and the superconducting condensate and can appear at frequencies predicted by conventional methods based on perturbations around the energy eigenstate of the time-independent system. The relevance of these non-perturbative processes to the operation of quantum logic gates based on superconducting circuits and the effect of the resultant non linearities on the environmental degrees of freedom coupled to the qubit are considered.