Method and apparatuses for filtering noise in a signal

Abstract

A method (100) for filtering noise in a signal, the method performed by a transmitter, a first device, and a second device in a telecommunications network. The method comprises the transmitted splitting the signal into a first and a second part and transmitting the first and second part to the first and second device. The first device passes the first part through a polarization rotator configured using a key shared with the second device. The key comprises indications for which polarization to select for each segment of the first part of the signal. The first device passes the first part through a first polarization splitter, the first polarization splitter configured using the key. The second device passes the second part through a second polarization splitter, wherein the second polarization splitter is configured using the key. A delay element is used to synchronize the first and second device.

Description

[0001] METHOD AND APPARATUSES FOR FILTERING NOISE IN A SIGNAL

[0002] TECHNICAL FIELD

[0003] The disclosure relates generally to a method for filtering noise in a signal, and further discloses a related noise amplifier, transceiver, and filter.

[0004] BACKGROUND

[0005] Telecommunication channels can only be established using technologies which can achieve a reasonably high signal-to-noise ratio, enabling transmitting significant amounts of data per unit time. Transmitting data using quantum microwave technologies has been limited by the necessity of cryogenic cooling of transmitter and receiver circuits to reduce thermal noise sufficiently to measure microwave photon energy. For example, in Microwave Quantum Link between Superconducting Circuits Housed in Spatially Separated Cryogenic Systems, P. Magnard, et. al., Phys. Rev. Lett. 125, 260502, 2020, https: / / arxiv.org / abs / 2008.01642v1 , spatially separated cryogenic systems were used to generate entanglement and transfer qubit states from a sender to a receiver. At optical frequencies, similar experiments can be performed at room temperature using fiber optic waveguides and standard components such as laser transmitters, polarizers, and receivers. However, transmitting a sufficiently strong signal is problematic.

[0006] More recently, Rydberg microwave receivers have seen significant research investment for potential improvements to receiver sensitivity and selectivity. However, how to use quantum technologies to create new types of radio channels with potential applications in future cellular networks such as 6G or any future generation is unknown.

[0007] SUMMARY

[0008] It is an object of the present disclosure to present a filtering method enabling a quantum radio channel.

[0009] According to a first aspect, there is a method for filtering noise in a signal, the method performed a transmitter, a first device, and a second device in a telecommunications system. The method comprises the transmitter splitting the signal into a first part and a second part, wherein the splitting comprises splitting entangled quantum system pairs. The method comprises the transmitter transmitting the first part of the signal to the first device and the first device receiving the first part of the signal. The method comprises the transmitter transmitting the second part of the signal to the second device and the second device receiving the second part of the signal. The method comprises the first device passing the first part of the signal through a polarization rotator, wherein the polarization rotator is configured using a key, wherein the key is shared between the first device and the second device, wherein the key comprises indications for which polarization to select for each segment of the first part of the signal. The method comprises the first device passing the first part of the signal though a first polarization splitter, wherein the first polarization splitter is configured using the key to obtain a filtered signal. The method comprises the second device passing the second part of the signal through a second polarization splitter, wherein the second polarization splitter is configured using the key to obtain the filtered signal. The first device or the second device use a delay element to synchronize the first part of the signal and the second part of the signal passing through the first polarization splitter and the second polarization splitter respectively.

[0010] According to a second aspect, there is a quantum noise amplifier comprising an input data stream, an output data stream, and a polarization splitter. The quantum noise amplifier is configured to receive a first part of a signal, the first part of the signal comprising one part of a split entangled quantum system. The quantum noise amplifier is configured to pass the first part of the signal through the polarization splitter, wherein the polarization splitter is configured using a key shared with a second device to obtain a filtered signal.

[0011] According to a third aspect, there is a radio transceiver comprising a polarization rotator, and a polarization splitter. The radio transceiver is configured to receive a first part of a signal, the first part of the signal comprising one part of a split entangled quantum system. The radio transceiver is configured to pass the first part of the signal through a polarization rotator, wherein the polarization rotator is configured using the key, wherein the key is shared between the transceiver and a second device, wherein the key comprises indications for which polarization to select for each segment of the first part of the signal. The radio transceiver is configured to pass the first part of the signal through a polarization splitter, wherein the polarization splitter is configured using the key, wherein the polarization splitter is configured to pass a first proportion of the polarization indicated by the key and a second proportion of the polarization not indicated by the key. Data is encoded for transmission to the second device by encoding binary data on the signal by selecting a polarization rotation for the polarization rotator which differs from the polarization rotation indicated by the key, wherein a first binary symbol is encoded as a first signal strength of the filtered signal and a second binary symbol is encoded as a second signal strength of the filtered signal.

[0012] According to a fourth aspect, there is a filter comprising at least one input and one output. The filter comprises a plurality of segmented transmission lines, each segment not less than 0.59A in length and not more than 100A in length. Each segment comprises a through line length, a polarization rotating transmission line, and a polarization passing filter. The filter comprises a filter input connected to the first segment and a filter output connected to the last segment, the segmented sections comprising at least one polarizing passing filter.

[0013] According to a fifth aspect there is a computer program comprising computer readable instructions, which, when executed by the processing circuitry of an apparatus, cause the apparatus to perform a method according to any embodiment of the first aspect.

[0014] According to a sixth aspect, there is a computer readable non-transient storage medium on which a computer program according to the fifth aspect is stored.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 is a flowchart of a method according to the disclosure.

[0017] Fig. 2 is an example of a polarization rotator according to the disclosure.

[0018] Fig. 3 is an example of a polarization splitter according to the disclosure.

[0019] Fig. 4 is a block diagram of a system implementing methods according to the disclosure.

[0020] Fig. 5 is a schematic overview of a telecommunications system in which methods according to the disclosure may be implemented.

[0021] DETAILED DESCRIPTION OF THE DRAWINGS The methods presented herein are an application of quantum microwave entanglement, that is, the nonclassical interdependency of physically separable quantum subsystems in the field of radio communications.

[0022] Methods presented herein comprise a high accuracy timing causal correlation, which may be referred to as a quantum noise amplifier (QNA). A signal comprising entangled quantum system pairs is split into two parts, where the splitting comprises splitting entangled quantum system pairs. The two parts of the signal, comprising entangled particles, are synchronized by the transmitter and the receiver and the signals passed through a polarization rotator configured using a shared key. This method, referred to as causal correlation, performs:

[0023] 1 . Filtering and discrimination of non-entangled electrons and improving a ratio of entangled quantum system pairs to non-entangled particles of the signal, thereby increasing the noise figure at a receiver, with an output signal which is largely compose of correlated noise as entangled electrons,

[0024] 2. The use of at least one key, shared between transmitter and receiver, to ensure a unique and secure causal correlation, where opposite keys are used in paired causal correlators ensure cancellation of polarization spin effects,

[0025] 3. The design of portions of the causal correlator to attenuate rather than pass signals, and the use of dynamic key changes to vary the amount of correlated noise signal power that is measured to transmit data.

[0026] 4. The operation of parallel causal correlators, with pairs of correlators carrying l / Q data, and multiple pairs carrying layers of transmission signals.

[0027] Embodiments herein include an end-to-end implementation of a novel radio channel based on this method which addresses important aspects necessary for causal correlation function to correctly operate, including:

[0028] • Mitigating Berry phase effects which cause polarization rotations in both the RBS and UE causal correlators,

[0029] • Accounting for the random initial polarizations arriving at the RBS and UE side, as the signal path will encounter multiple polarization rotations as correlated entangled electrons encounter over the air propagation reflections, or experience momentum changes in the delay lines at the transmitter.

[0030] While the keys used to code causal correlators could be changed after the measurement is made, the measurement outcome is determined from the previous history of the entangled photons.

[0031] In some embodiments, the keys remain static for the duration of the time from when the entangled electrons are generated to when they are measured, including any over-the-air propagation time.

[0032] Methods presented herein deliver a novel means of communications between a transmitter (e.g. a radio base station) and a receiver (e.g. a user equipment, UE) leveraging quantum causal correlations. This means of communication may be referred to as a quantum radio.

[0033] The proposed solution with a physical implementation with multiple polarization rotators polarization splitters / filters is able discriminate undesired signals by performing multiple, causal actions to increase the quantum gain, or squeezing parameter of the system.

[0034] The proposed solution, with its ability to perform quantum causal correlations at a rate (possibly 50ps) that is much faster than the measurement sample rate which for example may be 1 / 122.88MHz = 8ns, enables the quantum causal correlation process to complete (after 8ns / 50ps = 160 period, providing sufficiently large keys of 128 bits followed by 32-bit transitions of 3 dB, for a robust implementation.

[0035] The proposed solution, while intended to operate on a transmission stream of entangled electrons, may (potentially) have similar responses when operating from localized classical noise sources, as it may be that a portion of these noise sources includes entangled electrons. That is, the signal may, in some embodiments, comprise random environmental noise which is modulated by the sender and receiver using the causal correlation method as described herein to transmit data.

[0036] Fig. 1 is a flowchart of the causal correlation method as disclosed herein. The method 100 is a method for filtering noise in a signal, the method performed by a system comprising a transmitter, a first device, and a second device. The system is a telecommunication system, where the first device and the second device are nodes in a telecommunication network. By way of example, the first device may be a radio access node and the second device may be a wireless device / user equipment / communication device. In some embodiments, the transmitter is a third separate device and in other embodiments, the transmitter is a (logical or physical) module comprised in the first device or the second device.

[0037] The method comprises the transmitter splitting the signal into a first part and a second part, wherein the splitting comprises splitting entangled quantum system pairs. In some embodiments, the splitting may be performed by polarization, so that particles with a first polarization form the first part of the signal and particles with a second polarization form the second part of the signal. Entangled quantum system pairs may comprise entangled particle pairs, and in particular entangled particle pairs exhibiting distinct polarizations.

[0038] The method comprises the transmitter transmitting the first part of the signal to the first device. The method comprises the first device receiving the first part of the signal. The method comprises the transmitter transmitting the second part of the signal to the second device. The method comprises the second device receiving the second part of the signal.

[0039] The method comprises the first device passing the first part of the signal through a polarization rotator. The polarization rotator may be a polarization rotator as in Fig. 3, or any other suitable polarization rotator. The polarization rotator is configured using a key shared between the first device and the second device. The key comprises indications for which polarization to select for each segment of the first part of the signal. The segments of the signal comprise time periods of the signal: the first segment may for example comprise the first five picoseconds of the signal passing through the polarization rotator, and the second segment the next five picoseconds, and so on. In some embodiments, the key is pre-configured so that the rotations are determined by a fixed preamble shared between the first device and the second device or determined by a standard, such as a telecommunications standard. In some embodiments, the rotations may be accomplished using Berry phase rotations, resulting from implementing the method analogously to surface acoustic wave (SAW) or bulk acoustic wave (BAW) technology. The key thus comprises an indication of a list of agreed-upon rotations. One device uses the original key and the other device uses the inverse key, since the first part of the signal and the second part of the signal comprise parts of entangled quantum system pairs with opposite rotations.

[0040] The keys are used to pre-configure the causal correlation polarization splitters. These keys ensure secure communications between the network radio base station and UE with unique keys, which may vary over time. Keys in both the network and the UE ensure that causal correlations only occur when the keys match.

[0041] The causal correlation keys are valid only during the correlation time window to process the received signal at the correlation time window. The length of the correlation time window may be in the order of magnitude of picoseconds to nanoseconds. The quantum nature of the transmitted signal does not open the possibility for recording and post processing to uncover the keys, as the keys are no longer valid outside the correlation time window. This property of the proposed solution ensures an extremely high level of security in the quantum links, as signals cannot be intercepted and decoded at a later time.

[0042] The segments of the signal comprise segments of the wave split into time slots, where each time slot may comprise some pre-determined number of picoseconds. Filtering the signal is thus performed with one time slot at a time, so that classical (non-entangled) particles are filtered and with them the classical noise in the signal is also filtered.

[0043] The method further comprises the first device passing the first part of the signal through a first polarization splitter. The first polarization splitter is also configured using the key, and is configured so that it filters particles which have not been rotated.

[0044] The method further comprises the second device passing the second part of the signal through a second polarization splitter. The second polarization splitter is also configured using the key, and is configured so that it filters particles which have not been rotated in response to the rotation carried out with the first part of the signal.

[0045] The method further comprises the first device and / or the second device using a delay element to synchronize the first part of the signal and the second part of the signal passing through the first polarization splitter and the second polarization splitter respectively. Synchronizing the passing ensures that entangled particles pass though the polarization splitters at similar times, ensuring that as much entanglement as possible is preserved.

[0046] The delay element may comprise a length of transmission line, or it may be a gated delay element. In some embodiments, there may be some form of feedback between the first and second devices, and the delay element used to synchronize the first and second devices may operate entirely in the first device, or in the second device, or apportioned between these two devices.

[0047] The delay element enables precision timing between RBS and UE causal correlator circuits. The arrival times of the entangled electrons must be precisely aligned, since each of these waveguide sections is very short, e.g. a waveguide section only 10mm long represents 50 ps of time alignment. Note that the speed of light is 300 m / ps = 300 mm / ns = 0.3 mm / ps in air. In PCB material, the speed of light is slower, so if we assume 0.2 mm / ps a distance of 10 mm represents 50 ps of time.

[0048] Such precision is realized today using for example Ericsson’s UE Positioning RIBM timing solutions, coupled with SyncE phase locked loops. Moreover, it is currently planned to achieve this same level of precision timing in the macro network in time for an anticipated full scale 6G role out in 2030. The proposed method requires the transmitted and received signal correlations to be performed at the same time, aligned within picosecond, or at least nanoseconds depending on the delay designs of the correlation rotators and splitter elements.

[0049] To compensate for the UE specific over-the-air propagation time which must account for cell sizes of 500m for 100GHz operation, variable delay elements are required in the RBS and / or UE. The design of these delay elements is not detailed in this disclosure, but there are multiple means to implement such delay elements known in the art.

[0050] In preferred embodiments, the delay elements are located at the network side, with a high-power signal feed. At the UE side, the received signal may be attenuated by over the air pathlosses of perhaps 120 dB or more, resulting in signal levels which are in the range of ten billion times lower than the transmitted signal. As is generally known, gold-plated waveguides operating at 60 GHz have been verified to have losses of 4 dB / 30m, roughly 105 dB per 500m. Most of the losses in these waveguides are due to skin effect, and research has not been conducted in the space to reduce these effects. Similar to early optical fibers, it is expected that waveguide advancements will achieve lower loss, in similar ways as Coming introduced “large effective area fiber” or LEAF fiber which is central to today’s optical cable networks.

[0051] Other delay elements may be employed. Some research has proposed the use of gated transmission lines as a form of delay element. It is expected that capacitors, or other means may be used as a precision delay element. Regardless of the implementation, the delay element is a key requirement to ensure that the signals being processed at the two causal correlator elements arrive within a predefined and typically picosecond window of time to ensure that rotation causal elements or segments are aligned in absolute time with filter correlation elements or segments.

[0052] The method 100 may be performed several times to filter a maximal amount of noise from the signal. In some embodiments, the first device and the second device may alternate polarization rotations. In some embodiments, the first device and the second device may alternate which device perform the polarization rotations. The alternation may follow a pre-determined schedule.

[0053] The method 100 results in the first device and the second device obtaining a filtered signal where noise from classical unentangled particles has been filtered, thereby amplifying relative effect of the quantum noise of the signal. The first device or the second device performing the method 100 may be referred to as a quantum noise amplifier, QNA. A radio unit comprising a QNA or otherwise performing methods as presented herein, where the radio unit is compliant with a future telecommunications standard such as a 6G or 7G standard, may be referred to as a Quantum Radio, QR.

[0054] In some embodiments, the first polarization splitter and the second polarization splitter are configured to pass at least 90% of the polarization indicated by the key and approximately 50% of the polarization not indicated by the key. In some embodiments, a first proportion of the polarization indicated by the key is passed and a second proportion of the polarization not indicated by the key is passed by the first device, where the second proportion is determined relative the first proportion so that the second device will note a significant drop in signal strength if the wrong polarization is passed.

[0055] In such embodiments, the relative drop in signal strength may be used to encode binary information on the transmitted signal. Either the first device or the second device may encode information, as long as the device encoding information comprises a polarization rotator. Information may be encoded by the encoder selecting a different polarization rotation than indicated by the key, thereby causing a drop in signal strength for the receiving device. Note that the device referred to as the transmitter only provides the first signal and the second signal to the first and second device respectively. Encoding information and transmitting information does not involve the network node providing the signal, but rather only involves the two nodes transmitting and receiving. Hereby is achieved increased security for the transmitted messages. Moreover, since decoding the signal requires excellent synchronization with the sending device, the signal cannot be intercepted and stored for later decoding. The channel created by this method is hence very secure.

[0056] A higher signal strength may be selected to encode a first binary symbol and a lower signal strength may be selected to encode a second binary symbol. Each segment of the transmitted signal may thus correspond to one binary symbol.

[0057] Methods herein introduce the concept of causal correlation modulation as a means to transfer data from the network to the UE. This is made possible by dynamically changing a portion of the configured causal correlation key. Methods herein modify a portion of the series of preconfigured polarization rotators and splitters designed to pass both polarizations, with one attenuated by several dB, for example by 3 dB.

[0058] By configuring specific elements in the causal correlation keys, data may be transferred from the network to the UE, or from the UE to the network.

[0059] For example, if the network radio base station uses the key to configure all of its polarization rotators and splitters, and the UE uses the same key to correctly configure all of its polarization rotators and splitters, then the resulting measured signal seen at the UE has a value XUE.

[0060] If the network changes the configuration of one of its polarization rotators and splitters, wherein the changed configuration is specifically designed to pass the desired polarization at 100% and the alternate polarization at 50%, then the causal correlation natures of the link will result in a, for example, 3 dB reduction in measured signal when compared to the default with the correct key. This is to say that the UE will measure a signal level XUE - 3 dB which is distinguishable from the value XUE. The two distinct values can be used to encode binary data.

[0061] This methodology may equivalently be used to transmit data in the UE to network direction, simply by having the network radio base station transceiver employ the correct key, and the UE transceiver changing one of its polarization rotator and splitter key values. When the UE receiver key matches the Network Radio Base Station transmitter key, then the Network Radio Base Station measured output of the causal correlator will see a value of XRBS and if the UE receiver key changes a single element, so as to pass only 50% of the causal correlated signals, then the Network Radio Base Station measured output of the causal correlator will see a value of XRBS - 3 dB.

[0062] This method can then be used to transmit binary data from the Network RBS to the UE and vice versa by adjusting different portions of the causal correlation key. This binary data transmission may be labelled as an in-phase or “I” data stream. This is a linear example of how binary data may be coded into measured data. Alternate nonlinear compounding algorithms may be used to mitigate the detrimental effects of the limited dynamic range of the causal correlator passing and blocking of signals, in some embodiments limited to a dynamic range of 15 to 20 dB.

[0063] This method may be further extended by introducing a second causal correlation key, which is orthogonal to the first causal correlation key. These two keys would be used to transmit and receive separate and orthogonal data streams, so that independent data may be transmitted from Network RSB to UE and vice versa. This separate binary transmission stream may be labelled “Q” suggesting that it could represent quadrature-phase data.

[0064] The more accurately the first proportion and the second proportion are controlled by the polarization splitter, the higher the resolution of the resulting statistical measurement output and corresponding throughput.

[0065] In some embodiments, the first device and the second device share a first key and a second, wherein the first key and the second key are orthogonal. The two keys may be used to obtain a first filtered signal and a second filtered signal. The first filtered signal may be obtained by using the first key to filter the signal, and the second filtered signal may be obtained by using the second key to filter the signal. In such embodiments, two binary bit stream may be transmitted simultaneously over the single signal. For example, in-phase and quadrature component data, l / Q data, may be transmitted by using the first key to encode in-phase component data and the second key to encode quadrature component data of a wave function, where the wave function may be a wave function of a classic modulated radio signal.

[0066] Hence the concept of causal correlation modulation as a means to transfer data from the network to the UE may be used to transfer l / Q encoded data, aligning with 3GPP solutions.

[0067] The orthogonal aspect of causal correlation modulation can be extended yet again, from carrying an IQ modulated data stream to multiple IQ modulated data streams simply by using additional orthogonal keys. All of these inputs are possible with a single input and processed by multiple causal correlation modulation receivers. This new form of modulation is similar to MIMO only insofar as it offers the ability to send parallel data streams; however, it can be all transported through a single antenna element, hence, deriving the name for SIMO or single-input-multiple-output. The term SIMO makes a point that multiple data streams may be carried over the same channel using coding. It may also be referred to as QIMO, suggesting quantum- input- multiple-output.

[0068] The physical implementation of the method of Fig. 1 leverages two building blocks:

[0069] 1. a polarization splitter, and

[0070] 2. a polarization rotator.

[0071] Fig. 2 depicts an example of a polarization splitter.

[0072] The polarization splitter accepts any polarization, and through a binary control element, passes either one polarization or the other polarization.

[0073] In one embodiment, the polarization splitter and the polarization rotator are assumed to be developed using a circular waveguide. Electrical polarization splitters are known in the industry with many different implementations. Some implementations use magnetic fields to separate polarized electrons. Others modify the waveguide polarization properties, either the shape or through the use of gratings on the waveguide walls. Configurable quarter wave stubs protruding from the waveguide walls may be used to dynamically change permitted polarization that can pass.

[0074] The polarization splitter in Fig. 2 is shown as passing one polarization and terminating the other polarization, but this is not necessarily how such a circuit would be designed. In general, splitters such as the one depicted in Fig. 2 would achieve in excess of 20 dB isolation between streams, meaning that 99% of the undesired power would be terminated and 99% of the desired polarization would be passed through. However, with small design modifications, the polarization splitter could be designed to pass 50% of the undesired polarization and 99% of the desired polarization. In this way, the polarization splitter could be made to generate binary data output streams as in embodiments of the method 100. Described another way, the causal correlator can be used to generate statistical measurements of quantum entangled photons which differ based on the key configuration to enable coding and mapping to binary or other data streams.

[0075] Fig. 3 depicts an example of a polarization rotator in the form of a circular waveguide accepting a vertically polarized signal as shown with a TEn mode with the polarization pointing upwards.

[0076] In some embodiments, the polarization rotator is assumed to be developed using a circular waveguide, although this is strictly for illustrative purposes and many variations of the polarization rotator may be realized. The polarization rotator accepts a polarization and is configured to rotate the polarization by 90 degrees through a binary control element.

[0077] Configurable magnetic fields are applied externally to the waveguide, which is shrouded in a conducting, but nonferrous material allowing the magnetic fields to pass from one side of the waveguide to the other side.

[0078] At 9 GHz, a waveguide diameter is 10mm for 8.7 GHz cutoff frequency. At 90 GHz it is 1 mm diameter. At the anticipated frequency of 100 GHz and above, the proposed solution waveguide diameter would be less than 1mm, so that the magnetic field could be realized by small surface mount printed circuit board (PCB) components.

[0079] The example of Fig. 3 shows the TEn mode, shown above as a voltage gradient, which will rotate clockwise by 90 degrees as it tracks in orthogonal alignment to the preconfigured magnetic fields of the phase rotator. It is expected that at the 100 GHz frequency each polarization rotation may occur over segment lengths of 10mm representing a travel time of 50 picoseconds.

[0080] Note that the phase rotator may be programmed to one of three states: (1 ) rotate left; (2) rotate right; and (3) no rotation. Additional states of double rotate left, and double rotate right may be considered to result in phase rotations of 180 degrees. This rotation may be necessary in some embodiments to account for the unique properties of electrons.

[0081] Implementation of a magnetic polarization rotator would in many embodiments employ orthogonal magnets which can be fully, partially, or non-magnetized so that the aggregate magnetic fields would achieve the desired TEn field alignment. These configurable magnets or inductors are easily placed in a PCB structure.

[0082] The physical implementation includes a polarization rotator and splitter / filter at the Network RBS side, and the same at the UE side. The example in Fig. 4 shows the use case where both sides perform polarization rotations and polarization splitter / filters.

[0083] Note that the RBS side starts with a right polarized signal, which is rotated left using a polarization rotator. Below it, is the UE signal, passing through a circular waveguide and responding to the left rotation by a causal right polarization.

[0084] In the second segment, the UE is rotating the signal left, which is causing the RBS signal in the circular waveguide to causally rotate to the right. This is a causal correlation and only applies to entangled electrons.

[0085] It would not take many such rotations, each of which is followed by a polarization switch / f ilter that acts to discard non-entangled electrons unaffected by their causal partners before the resulting signal is largely entangled electrons. Fig. 4 is a schematic overview of a complete system of an RBS Transmitter with signal generation, timing and synchronization and quantum signal transmission / discrimination. At the UE is the reverse, with quantum signal reception / discrimination, timing and synchronization, and quantum signal detection.

[0086] Quantum causal coupling links the quantum correlators in the RBS (transmission I discrimination) and UE (reception I discrimination). Discrimination refers to classical electrons terminated by the polarization splitter in the RBS or the UE when they do not follow causal rotations.

[0087] It is known in the art to employ cryogenically cooled SQUID circuits to generate microwave signals with entangled electrons. In such implementations, the entangled electron output power is on the order of -83 dBm with a -17 dB SINR, and even so, a measurable signal could be transmitted.

[0088] However, cryogenic cooling is impractical and not viable for 6G communications, and the achieved quantum entanglement power levels are excessively low compared to traditional cell site power levels. Even achieving significant potential correlation gains of 78 dB if the proportion of entangled quantum systems in the signal can be driven to 90% (r=10), it is expected that 0 dBm is a minimum practical power level for any such feature, under the assumption that additional antenna gains can be realized.

[0089] In one embodiment, masers - microwave lasers and specifically, NV diamond masers - are used as the source of the transmitted signal. Nitrogen vacancy (NV) diamonds are now mainstream commercial components, employed for sensor applications where they have demonstrated practical usefulness. These commercially grown diamond crystals can be pumped with green laser light to release red light and maser energy from the ms= ±1 and ms= 0 transitions [Error! Reference source not found.].

[0090] An alternate and earlier room temperature maser is the pulsed pentacene: paraterphenyl maser. This maser was optically pumped with 230Wto deliver a -10 dBm maser output.

[0091] These findings suggest that at this point in time, until maser powers increase from - 50 dBm towards a potential target of 0 dBm, the proposed solution may not attain a commercially viable status. However, the method is achievable in research environments today, and high antenna gains of 40-50 dB at 100 GHz are quite viable, and NV Diamond maser technology is progressing very quickly.

[0092] Meanwhile, even at -50 dBm, methods herein may be useful for indoor applications where link budgets can readily handle the lower powers, and where high precision timing is already available.

[0093] On the receiver side, Rydberg receivers may be employed to enable extremely low power receiver sensitivity as a measurement sensor for the output of the quantum correlator. The reason is that the quantum correlator output may have signal powers which are close to thermal noise, and the ability to measure power from perhaps a few thousand electrons may improve receiver sensitivity. The National Institute for Standards and Technology (NIST) is investigating using Rydberg receivers for application as an atomic standard to calibrate electromagnetic fields. Lasers are used to excite Rydberg atoms electrons to high energy Rydberg states, where they become highly sensitive to microwave fields, whose presence causes shifts of the energy levels of the atoms. Shifts can be detected by monitoring absorption of a probe laser which is tuned to a lower energy state. Current Rydberg receiver research shows significantly higher noise figures than commercial low noise amplifiers (LNAs).

[0094] LNAs typically use field effect transistors (FET) to achieve high gain, low noise operation. The FETs are typically Silicon-Germanium (SiGe) based materials for radio frequency operation, but also advanced materials such as Indium Phosphide (InP) or Gallium Arsenide (GaAs) may be used for millimeter frequency applications.

[0095] Other types of receivers which may be used include masers (microwave amplification by stimulated emission of radiation) where the atoms are energized to excited states, enabling a received signal to trigger stimulated decay to a lower state resulting in microwave radiation emissions. Due to their cryogenic operational requirement, masers have seen limited application and are typically used only in areas requiring their low noise signal amplification performance, such as deep space radio astronomy. Recent advances in maser technology using nitrogen vacancy diamonds may yield a larger suite of applications.

[0096] Photon counting may be a possible receiver technology. While optical photon counters are used in industry, microwave photon counters require cryogenic cooling. However, if coupled with an electrical-to-optical conversion element such as a maser or Rydberg receiver, then optical photon counters have the potential to detect small numbers of microwave photons, such as counts of tens of photons.

[0097] Superconducting microwave photon detectors are possible, such as superconducting qubits, Josephson photomultipliers, as well as future receiver technologies which may be compatible with a system such as the one herein disclosed.

[0098] Fig. 5 is a schematic overview of a telecommunications system 500 in which methods oriented herein may be implemented.

[0099] The telecommunication network 500 that includes an access network 504, such as a radio access network (RAN), and a core network 506, which includes one or more core network nodes 508. The access network 504 includes one or more access network nodes, such as network nodes 510a and 510b (one or more of which may be generally referred to as network nodes 510), or any other similar 3rdGeneration Partnership Project (3GPP) access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network 500 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network 500 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network 500, including one or more network nodes 510 and / or core network nodes 508.

[0100] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU-CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an A1 , F1 , W1 , E1 , E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an 0-2 interface defined by the 0-RAN Alliance or comparable technologies. The network nodes 510 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 512a, 512b, 512c, and 512d (one or more of which may be generally referred to as UEs 512) to the core network 506 over one or more wireless connections.

[0101] The network nodes and or UEs may correspond to the first device and / or the second device and / or the transmitter of the method 100. In particular, in a first class of embodiments a radio access node corresponds to the transmitter and the first device, while a UE corresponds to the second device. Methods implemented according to the first class of embodiments establish quantum radio channels between a UE and a base station. In a second class of embodiments, the radio access node corresponds to the transmitter and the first and second device respectively correspond to a first and second UE. In methods implemented according to the second class of embodiments, the radio base station facilitates a quantum radio channel directly between the first and second UE. However, unlike a traditional radio channel, radio communications are transmitted directly between the UEs in a device2device type channel without passing through the radio base station. The radio base station simply provides the entangled signals for the UEs to modulate to transmit information.

[0102] Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the telecommunication network 500 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections in addition to the quantum radio channels according to the disclosure. The telecommunication network 500 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0103] The UEs 512 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with the network nodes 510 and other communication devices. Similarly, the network nodes 510 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs 512 and / or with other network nodes or equipment in the telecommunication network 502 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in the telecommunication network 502.

[0104] In the depicted example, the core network 506 connects the network nodes 510 to one or more hosts, such as host 516. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 506 includes one more core network nodes (e.g., core network node 508) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 508. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0105] As a whole, the telecommunication network 500 of Figure 5 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G, 7G, QR); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0106] In some examples, the telecommunication network 500 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 500 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 500. For example, the telecommunications network 500 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive loT services to yet further UEs. The quantum radio according to embodiments presented herein would then represent a further type of service offered to UEs.

[0107] In some examples, the UEs 512 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 504 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 504. Additionally, a UE may be configured for operating in single- or multi- RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[0108] In the example, the hub 514 communicates with the access network 504 to facilitate indirect communication between one or more UEs (e.g., UE 512c and / or 512d) and network nodes (e.g., network node 510b). In some examples, the hub 514 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 514 may be a broadband router enabling access to the core network 506 for the UEs. As another example, the hub 514 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 510, or by executable code, script, process, or other instructions in the hub 514. As another example, the hub 514 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 514 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 514 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 514 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 514 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0109] The hub 514 may have a constant / persistent or intermittent connection to the network node 510b. The hub 514 may also allow for a different communication scheme and / or schedule between the hub 514 and UEs (e.g., UE 512c and / or 512d), and between the hub 514 and the core network 506. In other examples, the hub 514 is connected to the core network 506 and / or one or more UEs via a wired connection. Moreover, the hub 514 may be configured to connect to an M2M service provider over the access network 504 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 510 while still connected via the hub 514 via a wired or wireless connection. In some embodiments, the hub 514 may be a dedicated hub - that is, a hub whose primary function is to route communications to / from the UEs from / to the network node 510b. In other embodiments, the hub 514 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 510b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0110] Filtering methods as presented herein may be performed by a filter comprising at least one input and one output. The filter further comprises a plurality of segmented transmission lines where each segment not less than 0.59A in length and not more than 100A in length. Each segment of the transmission lines comprises a through line length, a polarization rotating transmission line, and a polarization passing filter. The filter is configured so that a filter input is connected to the first segment and a filter output is connected to the last segment, and the segmented sections comprise at least one polarizing passing filter.

[0111] The transmission line may comprise one of: a circular waveguide with minimum waveguide diameter 0.59A, a rectangular waveguide with minimum broad width 0.59A, a coaxial transmission line, a stripline transmission line, a microstrip transmission line, or a parallel line such as a ladder or a twisted pair line.

[0112] In some embodiments, the polarization rotating transmission line has mechanical bends where the bends cause a Berry phase rotation. The Berry phase rotation may be one of: a left rotation, a right rotation, a double left rotation, a double right rotation, or no resulting rotation.

[0113] In some embodiments, the polarization rotating transmission line is one of: a left rotation, a right rotation, a double left rotation, a double right rotation, or no rotation.

[0114] In some embodiments, the polarization filter passes a portion of one of: a first polarization, a second polarization, or a first and a second polarization.

[0115] In some embodiments, the filter further comprises control circuitry to control the polarization rotation and / or the polarization filter.

[0116] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0117] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non- transitory computer-readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.

Claims

CLAIMS1. A method (100) for filtering noise in a signal, the method performed by a transmitter, a first device, and a second device, in a telecommunications network, the method comprising: the transmitter splitting (101 ) the signal into a first part and a second part, wherein the splitting comprises splitting entangled quantum system pairs; the transmitter transmitting (102) the first part of the signal to the first device; the first device receiving (103) the first part of the signal; the transmitter transmitting (104) the second part of the signal to the second device; the second device receiving (105) the second part of the signal; the first device passing (106) the first part of the signal through a polarization rotator, wherein the polarization rotator is configured using a key, wherein the key is shared between the first device and the second device, wherein the key comprises indications for which polarization to select for each segment of the first part of the signal; the first device passing (107) the first part of the signal though a first polarization splitter, wherein the first polarization splitter is configured using the key to obtain a filtered signal; the second device passing (108) the second part of the signal through a second polarization splitter, wherein the second polarization splitter is configured using the key to obtain the filtered signal. wherein the first device or the second device use a delay element to synchronize the first part of the signal and the second part of the signal passing through the first polarization splitter and the second polarization splitter respectively.

2. The method (100) according to claim 1 , wherein the first polarization splitter and the second polarization splitter are configured to pass 90% of the polarization indicated by the key and 50% of the polarization not indicated by the key.

3. The method (100) according to claim 1 , wherein the first polarization splitter and the second polarization splitter are configured to pass a first proportion of the polarization indicated by the key and a second proportion of the polarization not indicated by the key, wherein the first proportion and the second proportion are selected so that the filtered signal at the device not performing the polarization are clearly distinguishable in signal strength.

4. The method (100) according to claim 2 or 3, further comprising encoding binary data on the signal by the device performing the polarization rotation selecting a polarization rotation for the polarization rotator which differs from the polarization rotation indicated by the key, wherein a first binary symbol is encoded as a first signal strength of the filtered signal and a second binary symbol is encoded as a second signal strength of the filtered signal.

5. The method (100) according to claim 4, further comprising the transmitter and the receiver having a second key, the second key being orthogonal to the first key, the second key being used to filter a second filtered signal from the signal.

6. The method (100) according to claim 5, further comprising the transmitter encoding in-phase and quadrature component data, l / Q data, on the signal, where the in-phase component is encoded using the first key and the quadrature component is encoded using the second key.

7. A quantum noise amplifier comprising an input data stream, an output data stream, and a polarization splitter (300), the quantum noise amplifier configured to: receive a first part of a signal, the first part of the signal comprising one part of a split entangled quantum system; pass the first part of the signal through the polarization splitter (300), wherein the polarization splitter is configured using a key shared with a second device to obtain a filtered signal.

8. The quantum noise amplifier according to claim 7, further comprising a polarization rotator (200), the quantum noise amplifier configured to: pass the first part of the signal through a polarization rotator, wherein the polarization rotator is configured using the key, wherein the key is shared betweenthe first device and the second device, wherein the key comprises indications for which polarization to select for each segment of the first part of the signal.

9. The quantum noise amplifier according to claim 7 or 8, wherein the quantum noise amplifier is comprised in a radio base station or a user equipment.

10. A radio transceiver (401 , 402) comprising a polarization rotator (200), and a polarization splitter (300), the radio transceiver configured to: receive a first part of a signal, the first part of the signal comprising one part of a split entangled quantum system; pass the first part of the signal through a polarization rotator, wherein the polarization rotator is configured using the key, wherein the key is shared between the transceiver and a second device, wherein the key comprises indications for which polarization to select for each segment of the first part of the signal; pass the first part of the signal through a polarization splitter, wherein the polarization splitter is configured using the key, wherein the polarization splitter is configured to pass a first proportion of the polarization indicated by the key and a second proportion of the polarization not indicated by the key; wherein data is encoded for transmission to the second device by encoding binary data on the signal by selecting a polarization rotation for the polarization rotator which differs from the polarization rotation indicated by the key, wherein a first binary symbol is encoded as a first signal strength of the filtered signal and a second binary symbol is encoded as a second signal strength of the filtered signal.11 . The transceiver (401 , 402) according to claim 10, wherein the transceiver has a second key shared with the second device, the second key being orthogonal to the first key, wherein the transceiver is configured to encode a second signal to the second device using the second key.

12. The transceiver (401 , 402) according to claim 11 , further configured to encode in-phase and quadrature component data, l / Q data, on the signal, where the in-phase component is encoded using the first key and the quadrature component is encoded using the second key.

13. The transceiver (401 , 402) according to any one of claims 10-12, wherein the radio transceiver is comprised in a radio base station or a user equipment.

14. A filter comprising at least one input and one output, the filter comprising a plurality of segmented transmission lines, each segment not less than 0.59A in length and not more than 100A in length, each segment comprising: a through line length; a polarization rotating transmission line; and a polarization passing filter, a filter input connected to the first segment and a filter output connected to the last segment, the segmented sections comprising at least one polarizing passing filter.

15. The filter according to claim 14, wherein the transmission line is one of: a circular waveguide with minimum waveguide diameter 0.59A; a rectangular waveguide with minimum broad width 0.59A; a coaxial transmission line; a stripline transmission line; a microstrip transmission line; or a parallel line such as a ladder or a twisted pair line.

16. The filter according to claim 14 or 15, wherein the polarization rotating transmission line has mechanical bends, the bends causing a Berry phase rotation which is one of: a left rotation; a right rotation; a double left rotation; a double right rotation; or no resulting rotation.

17. The filter according to any one of claims 14-16, wherein the polarization rotating transmission line is one of: a left rotation; a right rotation; a double left rotation; a double right rotation; or no rotation.

18. The filter according to any one of claims 14-17 wherein the polarization filter passes a portion of one of: a first polarization; a second polarization; or a first and a second polarization.

19. The filter according to any one of claims 14-18, further comprising control circuitry to control the polarization rotation and / or the polarization filter.

20. The filter according to any one of claims 14-19, wherein the filter is comprised in a radio base station or a user equipment.21 . A computer program comprising computer readable instructions which, when executed by processing circuitry of an apparatus, cause the apparatus to perform a method according to any one of claims 1-6.

22. A computer-readable non-transient storage medium upon which a computer program according to claim 21 is stored.

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