EP4717012A1 - Quantum communication of data using a distributed entanglement state - Google Patents
Quantum communication of data using a distributed entanglement stateInfo
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- EP4717012A1 EP4717012A1 EP24742583.8A EP24742583A EP4717012A1 EP 4717012 A1 EP4717012 A1 EP 4717012A1 EP 24742583 A EP24742583 A EP 24742583A EP 4717012 A1 EP4717012 A1 EP 4717012A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/70—Photonic quantum communication
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Abstract
Disclosed is a method of transmitting data from a sender quantum processing unit to a receiver quantum processing unit comprising: encoding the data to be transmitted from the sender quantum processing unit to the receiver quantum processing unit, the encoding comprising mapping the data into a range of rotation angle values for obtaining a rotation angle encoding the data, receiving a sign of the rotation angle by the receiver quantum processing unit; repeatedly performing: creating the distributed entangled state, transforming the qubit state of the sender qubit by the rotation angle, measuring the sender qubit and receiver qubit and storing a tuple comprising the measured sender and receiver states; calculating by the receiver quantum processing unit the rotation angle using the sign of the rotation angle and the stored tuples of the sender and the receiver states, decoding the rotation angle for obtaining the data by the receiver quantum processing unit.
Description
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - QUANTUM COMMUNICATION OF DATA USING A DISTRIBUTED ENTANGLEMENT STATE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - FIELD OF THE INVENTION [0001]The invention relates to the field of data communication, and particularly to a method for quantum communication of data using a distributed entanglement state. BACKGROUND [0002]Quantum communication is a field that uses the quantum mechanical properties of a quantum system; properties like superposition and entanglement, to enable secure and efficient communication protocols. It offers a wide range applications like Quantum Key Distribution (QKD) which enables two parties to securely exchange cryptographic keys between them, wherein any attempt to intercept the quantum signal by a third party will disturb the quantum state, alerting the legitimate users. Another major application of quantum communication is the quantum teleportation and quantum cryptography. However, there is a need for improved use of quantum teleportation. SUMMARY [0003]It is an objective to provide a method for quantum communication of data using a distributed entanglement state. The objectives underlying the invention are solved by the features of the independent claims. [0004]Embodiments provide a method of transmitting data from a sender quantum processing unit to a receiver quantum processing unit is provided. The method comprises encoding the data to be transmitted from the sender quantum processing unit to the receiver quantum processing unit, the encoding comprising mapping the data into a range of rotation angle values for obtaining a rotation angle encoding the data, receiving a sign of the rotation angle by the receiver quantum processing
unit; repeatedly performing: forming a distributed entanglement state between a sender qubit in the sender quantum processing unit and a receiver qubit in the receiver quantum processing unit; and thereafter transforming a qubit state of the sender qubit by the rotation angle; measuring the sender qubit, resulting in a sender state of the sender qubit; receiving by the receiver quantum processing unit the sender state; measuring the receiver qubit, resulting in a receiver state of the receiver qubit; and storing a tuple of the sender state and the receiver state; and calculating the rotation angle using the sign of the rotation angle and the stored tuples of the sender and the receiver states, decoding the rotation angle for obtaining the data by the receiver quantum processing unit. [0005]Embodiments provide a method (sending method) of transmitting data from a sender quantum processing unit to a receiver quantum processing unit. The method comprises at the sender quantum processing unit encoding the data to be transmitted from the sender quantum processing unit to the receiver quantum processing unit, the encoding comprising mapping the data into a range of rotation angle values for obtaining a rotation angle encoding the data, sending a sign of the rotation angle to the receiver quantum processing unit; repeatedly performing: forming a distributed entanglement state between a sender qubit in the sender quantum processing unit and a receiver qubit in the receiver quantum processing unit; and thereafter transforming a qubit state of the sender qubit by the rotation angle; measuring the sender qubit, resulting in a sender state of the sender qubit; sending the sender state to the receiver quantum processing. [0006]Embodiments provide a method (receiving method) of transmitting data from a sender quantum processing unit to a receiver quantum processing unit. The method comprises at the receiver quantum processing unit: receiving a sign of the rotation angle by the receiver quantum processing unit, the rotation angle encoding the data; repeatedly performing: receiving a sender state of a sender qubit in the sender quantum processing unit wherein the sender qubits is in a distributed entanglement state with a receiver qubit in the receiver quantum processing unit; measuring the receiver qubit, resulting in a receiver state of the receiver qubit; storing a tuple of the sender state and the receiver state; calculating the rotation angle using the sign of the rotation angle and the stored tuples of the sender and
the receiver states, decoding the rotation angle for obtaining the data by the receiver quantum processing unit. [0007]Embodiments provide a method of transmitting data from a sender quantum processing unit to a receiver quantum processing unit. The method comprises the sender quantum processing unit which is configured to perform the sending method and the receiver quantum processing unit which is configured to perform the receiving method. [0008]It is understood that one or more of the aforementioned embodiments may be combined as long as the combined embodiments are not mutually exclusive. BRIEF DESCRIPTION OF THE DRAWINGS [0009]In the following, examples are described in greater detail making reference to the drawings in which: [0010]Fig.1 is a block diagram a quantum communication system in accordance with the preferred embodiment of the present invention. [0011]Fig.2 is a flowchart of a method for transmitting data from a sender quantum processing unit to a receiver quantum processing unit. [0012]Fig.3 is a flowchart of a method of calculating a rotation angle. [0013]Fig.4 is a flowchart of a method of calculating a rotation angle. [0014]Fig.5 is a flowchart of a method of transmitting data from a sender quantum processing unit to a receiver quantum processing unit. [0015]Fig.6 show graphs of the distributions of the measured states of the receiver qubit for distinct states of the sender qubit. DETAILED DESCRIPTION [0016]In the following, similar elements are denoted by the same reference numerals.
[0017] The present subject matter may enable two or more distant parties to communicate securely with each other. This communication may be useful in a wide range of applications where security may be critical, such as in financial transactions, government communications, and military operations. For that, a multi-qubit system may be used. The multi-qubit system may comprise at least the sender quantum processing unit and the receiver quantum processing unit. The sender quantum processing unit may be a quantum processing unit. The receiver quantum processing unit may be a quantum processing unit. The quantum processing unit (QPU) may be a component that may be used to perform quantum computations by operating one or more qubits. The quantum processing unit may further comprise a classical processing component. The classical processing component may, for example, control the qubit(s) to perform quantum operations on the qubits. [0018]The sender qubit of the sender quantum processing unit may be a qubit. The receiver qubit of the receiver quantum processing unit may be a qubit. The qubit may exist in a superposition of two states, wherein the two states may be referred to respectively as l0˃ and l1˃ in accordance with the Dirac notation. The state l0˃ may be named as first state and l1˃ may be named as second state. The terms “First,” and “Second,” are used as labels for nouns that they precede, and do not imply any type of ordering (e.g., spatial, temporal, logical) unless explicitly defined as such. The qubit may physically be implemented using a quantum system having two states such as a photon and ion. For example, the vertical and horizontal photon’s polarization may be used as a qubit state. The two energy levels of an ion may be used as a qubit state. [0019]The state of the multi-qubit system may be an entangled state. In the entangled state, the states of the multi-qubit system may not be factored. For example, in case of a two-qubit system, the entangled state of the two-qubit system may be any one of the Bell states. The present subject matter may make use of the entangled state of the multi-qubit system to transmit data. For that, the entangled state may be provided as a distributed entangled state such that the entangled sender qubit and receiver qubit are located at different locations in the respective sender quantum processing unit and the receiver quantum processing unit. The
distributed entangled state between the sender qubit and the receiver qubit may, for example, be formed by first forming locally e.g., at the sender quantum processing unit, the entangled state of the sender qubit and the receiver qubit, and subsequently sending the receiver qubit by the sender quantum processing unit to the receiver quantum processing unit. The entangled state may, for example, be formed by applying a CNOT operation on the sender qubit and the receiver qubit. [0020]The quantum communication is performed by repeatedly performing a method (herein named measurement method). The measurement method comprises: creating the distributed entangled state, transforming the qubit state of the sender qubit by the rotation angle, measuring the sender qubit and receiver qubit, and storing a tuple comprising the measured states of the sender qubit and receiver qubit. The transformation of the qubit state of the sender qubit may be implemented depending on the type of qubits being used. For example, the transformation may be performed by using a laser pulse for rotating the qubit state of the sender qubit by the rotation angle. The measurement method may be repeated until a stopping criterion is fulfilled. The stopping criterion may, for example, require a minimum number of repetitions. The minimum number of repetitions may enable to obtain accurate results. For example, if the measurement method is repeated ten times, this may result in ten tuples. In the case of a two- qubit system, each tuple may comprise a pair of qubit states, e.g. (|0>, |1>), (|1>, |1>) etc., wherein the first entry of the tuple may represent the state of the sender qubit, and the second entry may represent the state of the receiver qubit. After completing the repeated execution of the measurement method, the resulting tuples may be used to compute the rotation angle. The rotation angle may enable to recover data that is transmitted by the sender quantum processing unit. [0021]Hence, the information (such as tokens, numbers, etc.) may be transferred in a secure way. The information may not be copied due to the No Cloning Theorem. The information does not travel over a communication channel, but it is teleported from the sender qubit to the receiver qubit by means of entanglement. This may prevent attacks such as the “store now, decrypt later” attacks. In addition, the present method may straightforwardly be implemented as no complex and computationally intensive cryptographic operations may have to be carried out.
[0022]According to one example, the calculation of the rotation angle comprises: selecting stored tuples which comprise a selected state of the sender qubit, counting the number of measured first states of the receiver qubit and the number of measured second states of the receiver qubit from the selected tuples at the receiver quantum processing unit, and using the counted numbers to calculate the rotation angle. The calculation of the rotation angle may, for example, be performed by the classical processing component. [0023]For example, one of the two states of the sender qubit may be selected. The selection may be a random selection or based on a selection criterion. The stored tuples which have in the first entry the selected state may be identified. The second entries of the identified tuples may be processed to count the number of first states in these second entries and the number of second states in these second entries. For example, if the selected state of the sender qubit is the first state |0>, the number of measured first states of the receiver qubit may be referred to as ^^ and the number of measured second states of the receiver qubit may be referred to as ^^. If the selected state of the sender qubit is the second state |1>, the number of measured first states of the receiver qubit may be referred to as ^^ and the number of measured second states of the receiver qubit may be referred to as ^^. Thus, the rotation angle may be computed using the counted numbers ^^ and ^^ or using the counted numbers ^^ and ^^. The counted numbers ^^ and ^^ (or ^^ and ^^) may represent the probability of the receiver qubit is in the state |0> and |1> respectively. [0024]This example may provide an accurate determination of the rotation angle based on distributions of the measurements. The accuracy of the determined angle may be controlled according to the present subject matter by controlling the number of repetitions of the measurement method. This example may further be advantageous because the information is encoded at the sender quantum processing unit and decoded only by the receiver quantum processing unit, thereby transmitting the data with high security. [0025]In one example, the calculation of the rotation angle comprises: for each distinct state of the sender qubit: selecting stored tuples which comprises the distinct state of the sender qubit, counting the number of measured first state of the
receiver qubit and the number of measured second state of the receiver qubit from the selected tuples at the receiver quantum processing unit; using the counted numbers to calculate an individual rotation angle; combining the individual rotation angles for calculating the rotation angle. [0026]By contrast to the previous example, this example may compute the rotation angle using both pairs (^^, ^^) and (^^, ^^). Indeed, for two distinct states (|0> and l1˃) of the sender qubit, two individual rotation angles may be obtained respectively using the pairs (^^, ^^) and (^^, ^^). One individual rotation angle for the distinct state |0> and another individual rotation angle for the distinct state |1>. The final rotation angle may be obtained by combining the individual rotation angles. The combination of the individual rotation angles may, for example, be an average of the individual rotation angles or a weighted average of the individual rotation angles. [0027]This example may be advantageous because the rotation angle is calculated combinedly using each individual rotation angle. Combination of all such obtained individual rotation angle values may provide more accurate results because a higher number of measurements may be used to compute the rotation angle. [0028]According to one example, the counted numbers may be normalized before computing the rotation angle. The normalization may be performed, for example, to one. Normalizing the counted numbers may be a key feature in quantum communications to maintain the integrity of quantum states, preserve probabilities and enable valid quantum operations. Normalization may guarantee that the combined quantum states of entangled systems have a total probability of one. [0029]According to one example, the forming of the distributed entanglement state is performed at the sender quantum processing unit, wherein the entangled receiver qubit is received by the receiver quantum processing unit through a quantum channel. The entangled receiver qubit may be sent by the sender quantum processing unit to the receiver quantum processing unit through the quantum channel. The quantum channel may be provided depending on the type of qubits of the multi-qubit system. The quantum channel may, for example, be a dark optical fiber channel over which photonic quantum states may be transmitted. In one example, the quantum channel may be a wireless channel or a vacuum tube
between the sender quantum processing unit and the receiver quantum processing unit over which quantum states may be transmitted by ion transmission. [0030]Using quantum channels may be advantageous in many aspects. Quantum channels may offer a higher level of security, speed, and efficiency. In case of a hacker attempts to measure the receiver qubit being transmitted, the quantum state of the receiver qubit may be disturbed, alerting the sender and receiver to the presence of the hacker. Besides, quantum channels can transmit data at rates of up to several gigabits per second, making them ideal for high-speed communication applications. Quantum channels may allow for the transmission of information without any loss of signal strength due to attenuation or interference, allowing quantum channels to be highly efficient in terms of amount of information they can transmit. [0031]According to one example, the encoding of the data may be performed by at least: defining a unitary transformation representing one rotation operation of the qubit state of the sender qubit. The unitary transformation comprises trigonometric functions of the rotation angle. The unitary transformation may describe how the quantum state of the sender qubit evolves over time, taking an initial quantum state into account and transforming it into a final state, while preserving the probability of measuring any particular outcome. [0032]According to one example, the unitary transformation may be defined as a
where α is the rotation angle. Such matrix may perform one rotation operation of the qubit state of the sender qubit. In one example, the range of the rotation angle comprises values between -90 degrees to ^ ^ +90 degrees (or - ^ to + ^ radians). The restriction of the rotation angle to this range may prevent redundant representations of rotations. [0033]The rotation angle ^ may be obtained by mapping the data to be transmitted into a range of rotation angle values for obtaining the rotation angle ^ encoding the data. According to one example, the mapping of the data is performed by applying a minmax scaler to the data. A minmax scaler in context of quantum communication is applied to the data to scale the data within a specific range. By scaling the data
into this range, it is later beneficial for certain algorithms or analysis techniques to decode the data and extract the information thereby. [0034]In one example, mapping the data into a rotation angle is performed at the sender quantum processing unit. This may significantly be important in the case of quantum communication as the qubits are entangled in this unit wherein the entangled receiver qubit is further transferred to receiver quantum processing unit through the quantum channel. The data is then encoded in the rotation angle at the sender quantum processing unit. Applying a unitary transformation transforms the sender state of the sender qubit which along with the sign of the rotation angle may be sent to the receiver quantum processing unit. [0035]The present subject matter may make use of more than two qubits for data communication. For that, according to one example, the distributed entanglement state is formed between the sender qubit and the receiver qubit and an additional sender qubit. The additional sender qubit is part of an additional quantum processing unit. In this case, a qubit state of the additional sender qubit may also be transformed by the rotation angle ^. The additional sender qubit may be measured which may result in a sender state of the additional sender qubit. The receiver quantum processing unit may receive the sender state of the additional sender qubit so that the stored tuple further comprises the sender state of the additional sender qubit. The entangled state may, for example, be a Greenberger– Horne–Zeilinger state (GHZ-state). [0036]A quantum communication system comprising the sender qubit and the receiver qubit and the additional sender qubit in the additional quantum processing unit may enable secure transmittance of the data simultaneously from two distant locations which may be very useful in quantum communications channels, for example in quantum network applications. [0037]For example, the multi-qubit system is a three-qubit system comprising the two sender qubits and the receiver qubit. In this case, each tuple may comprise a triplet of the states of the two sender qubits and the receiver qubit. For example, the tuple may comprise, e.g. (|0>, |1>, |1>), (|1>, |1>, |0>) etc., wherein the first two
entries of the tuple represent the states of the sender qubits and the third entry represents the state of the receiver qubit. [0038]According to one example, the calculation of the rotation angle comprises: selecting stored tuples which comprise a selected state of the sender qubit and the additional sender qubit, counting the number of measured first state of the receiver qubit and the number of measured second state of the receiver qubit from the selected tuples at the receiver quantum processing unit, and using the counted numbers to calculate the rotation angle. [0039]For example, the two sender qubits may be in any one of the four states |00>, |01>, |10> and |11>. For example, one of the four states of the sender qubits may be selected. The selection may be a random selection or based on a selection criterion. The stored tuples which have in the first entry and the second entry the selected state may be identified. The third entries of the identified tuples may be processed to count the number of first states in these third entries and the number of second states in these first entries. For example, if the selected state of the sender qubits is |00>, the number of measured first states of the receiver qubit may be referred to as ^^^ and the number of measured second states of the receiver qubit may be referred to as ^^^. If the selected state of the sender qubits is the second state |01>, the number of measured first states of the receiver qubit may be referred to as ^^^ and the number of measured second states of the receiver qubit may be referred to as ^^^. If the selected state of the sender qubits is the second state |10>, the number of measured first states of the receiver qubit may be referred to as ^^^ and the number of measured second states of the receiver qubit may be referred to as ^^^. If the selected state of the sender qubits is the second state |11>, the number of measured first states of the receiver qubit may be referred to as ^^^ and the number of measured second states of the receiver qubit may be referred to as ^^^. Thus, the rotation angle may be computed using at least one of the pairs (^^^, ^^^), (^^^, ^^^), (^^^, ^^^) and (^^^, ^^^). [0040]In one example, the sender and the receiver qubits comprise trapped ions. This may enable the separation of the qubits by shooting. Two-ion traps may particularly be significant for example in the field of quantum computing and quantum information processing as they allow for the implementation of two-qubit
gates and entanglement operations. Various techniques can be employed to manipulate and control the ions, such as entanglement generation, gate operations and measurement. The so generated entangled qubits in this case may be separated by shooting laser of pulse frequency of 20000/s. In one example, the sender and the receiver qubits comprise photonic qubits. [0041] In one example, the transmitted data from the sender quantum processing to the receiver quantum processing unit may comprise any one of: a number, a certificate, a key, a token, a public key and a private key. This may enable a wider application of the present method. [0042]For example, the present method may be used for performing data transmissions in a Hardware Security Module (HSM) migration as described in patent application EP2454702A1. For example, a migration method may be provided for migrating from a first HSM to a second HSM, wherein the first HSM is associated with a first asymmetrical cryptographic key pair having a first personal key and a first public key and a first certificate containing the first public key, wherein the migration method comprises the following steps: generating a second asymmetrical cryptographic key pair having a second personal key and a second public key and a second certificate, which contains the second public key, by the second HSM, transmitting the second certificate with the second public key from the second HSM to the first HSM, and generating a third certificate by the first HSM by signing the second public key using the first personal key, wherein a certificate check of the second certificate can be carried out by way of a certificate chain containing the first and third certificates. [0043]The present method may be used for transmission of data in the migration process. The second HSM may be on the side of the sender quantum processing unit and the first HSM may be on the side of the receiver quantum processing unit, wherein the second certificate and/or the second public key may be encoded in rotation angles and transmitted in accordance with the present method. This may enable a secure migration of HSMs.
[0044]FIG.1 is a diagram of a quantum communication system 100 for transmitting data using quantum communication in accordance with an example of the present subject matter. [0045]The quantum communication system 100 comprises a sender quantum processing unit 103 and a receiver quantum processing unit 105. The sender and quantum processing units 103 and 105 may communicate through one or more communication channels. For example, the sender quantum processing unit 103 and the receiver quantum processing unit 105 may communicate through a quantum channel 104. [0046]The sender quantum processing unit 103 may comprise a sender qubit 110. The receiver quantum processing unit 105 may comprise a receiver qubit 111. In this example, the sender and receiver qubits may be in an entangled state. The entangled state between the sender qubit 110 and the receiver qubit 111 may be created at the sender quantum processing unit 103. The resulting receiver qubit 111 may be sent by the sender quantum processing unit 103 to the receiver quantum processing unit 105 through the quantum channel 104. [0047]The sender quantum processing unit 103 may comprise a classical computing component e.g., comprising a CPU and FPGA. The receiver quantum processing unit 105 may comprise a classical computing component e.g., comprising a CPU and FPGA. [0048]The sender quantum processing unit 103 comprises a data encoder 112. The data encoder 112 may be configured to encode the data to be transmitted from the sender quantum processing unit 103 to the receiver quantum processing unit 105. The encoder 112 may encode the data by mapping the data into a range of rotation angle values for obtaining a rotation angle 113 encoding the data. The mapping may, for example, be performed by using a minmax scaler. [0049]The sender quantum processing unit 103 may transform the state of the sender qubit 110 by the rotation angle 113. The transformation may be performed by using a laser pulse for rotating the qubit state of the sender qubit by the rotation angle. The rotation angle may be defined by a rotation matrix in the vector space of
the qubit states, where the rotation matrix may ensure that the quantum evolution of the system is unitary. [0050] After transforming the state of the sender qubit 110, the sender qubit 110 may be measured in order to obtain the state of the sender qubit 110. The measurement may collapse the entanglement state. The measured state may be sent by the sender quantum processing unit 103 to the receiver quantum processing unit 105. [0051]The state of the receiver qubit 111 may be measured and the pair of states of the sender and receiver qubits may be stored as a tuple. [0052]After repeating the measurement method multiple times, the rotation angle 113 may be determined (106) at the receiver quantum processing unit 105. The rotation angle 113 determination may be performed using the sign of the rotation angle 113. The sign of the rotation angle may be sent by the sender quantum processing unit 103 through a classical communication channel to the receiver quantum processing unit 105. FIG.6 provides an example method for determining the rotation angle 113. [0053]FIG.2 is a flowchart of a method for transmitting data from a sender quantum processing unit to a receiver quantum processing unit. In step 201, the data to be transmitted from the sender quantum processing unit to the receiver quantum processing unit is encoded in a rotation angle. The encoding comprises mapping the data into a range of rotation angle values for obtaining an angle encoding the data. In step 202, a sign of the rotation angle is received by the receiver quantum processing unit. The rotation angle is sent by the sender quantum processing unit to the receiver quantum processing unit. In step 203, a distributed entanglement state between a sender qubit in the sender quantum processing unit and a receiver qubit in the receiver quantum processing unit is formed. In step 204, a qubit state of the sender qubit is transformed by the rotation angle. In step 205, a sender state of the sender qubit is measured. In step 206, the sender state is received by the receiver quantum processing unit. In step 207, the receiver state of the receiver qubit is measured. In step 208, a tuple of the sender state and the receiver state is stored. It may be determined in step 209 whether a stopping criterion is fulfilled. In
case the stopping criterion is not fulfilled, steps 203 to 208 may be repeated; otherwise step 210 may be performed. In step 210, the rotation angle may be calculated using the sign of the rotation angle and stored tuples. And, the rotation angle may be decoded for obtaining the transmitted data. For example, the logic of the data mapping (e.g., minmax scaler) used to encode the data may be inverted in order to recover the data from the rotation angle. [0054]FIG.3 is a flowchart of a method of calculating the rotation angle 113. In step 301, stored tuples which comprise a given state of the sender qubit are selected. In step 302, the number of measured first states of the receiver qubit and the number of measured second states of the receiver qubit in the selected tuples are counted. In step 303, the rotation angle is calculated using the counted numbers. [0055]FIG.4 is a flowchart of a method of calculating the rotation angle 113. For each distinct state of the sender qubit steps 402 to 404 may be performed. In step 402, stored tuples which comprise the distinct state of the sender qubit is selected. In step 403, the number of measured first states of the receiver qubit and the number of measured second states of the receiver qubit in the selected tuples is counted. In step 404, an individual rotation angle is calculated using the counted numbers. In step 405, the rotation angle is calculated by combining the individual rotation angles. [0056]FIG.5 is a flowchart of a method of transmitting data from a sender quantum processing unit to a receiver quantum processing unit. The method may be performed using a sender quantum processing unit 501 and a receiver quantum processing unit 502. In step 503, data is encoded in a rotation angle 113 at the sender quantum processing unit. In step 504, sender qubit at the sender processing unit is transformed by applying a rotation angle. In step 505, the sender qubit is measured at the sender quantum processing unit. In step 506, the sign of rotation angle is sent from the sender quantum processing unit to the receiver quantum processing unit. In step 507, sender state of the sender qubit is sent from the sender quantum processing unit to the receiver quantum processing unit. In step 508, the receiver qubit is measured. In step 509, a tuple of the sender state and the receiver state is stored at the receiver quantum processing unit. The measurement method may be repeated for obtaining multiple tuples. In step 510, the rotation angle is
calculated using the tuples at the receiver quantum processing unit and in step 511, the rotation angle is decoded to obtain the data at the receiver quantum processing unit. [0057]FIG. 6 shows graphs representing the number of measured states of the receiver qubit in the system as shown in FIG.1. The transmitted data is encoded in the rotation angle ^ and the measurement method is repeated multiple times in order to obtain the graphs 601 and 602. [0058]Graph 601 represents the number (^^) of measured first states of the receiver qubit and the number (^^) of measured second states of the receiver qubit in case the sender qubit is in the first state |0>. [0059]Graph 602 represents the number (^^) of measured first states of the receiver qubit and the number (^^) of measured second states of the receiver qubit in case the sender qubit is in the second state |1>. [0060]The rotation angle ^ may be computed using the pair of numbers (^^, ^^) and/or the pair of number (^^, ^^). For that, the transformation of the sender qubit state may be modelled as follows. [0061]If the entangled state is the Bell state
+ |1> ⊗|1>), a unitary operation D which encodes the data may be used. The unitary operation
unitary matrix. [0062]The unitary operation D may be applied on the Bell state, meaning that the sender state is rotated with the angle ^ while the “one” operation is applied on the state of the receiver qubit. This may result into: D
((^^ |0>) ⊗ |0>) + (^^ |1>) ⊗ |1>). In addition, the application of the unitary matrix operation on the states of the sender qubit may be defined as follows: ^^ |0> = cos ^ |0> + sin ^ |1> and ^^ |1> = - sin ^ |0> + cos ^ |1>. The final expression for the transformed Bell state may thus be provided as follows: D
(|0> (cos ^ |0> - sin ^ |1>) + |1>(sin ^ |0> + cos ^ |1>). This model may provide state probabilities of the sender and receiver qubits. For example, this model indicates that the probability to have the sender
qubit in the first state and the receiver qubit in the first state is ^^^^α, the probability to have the sender qubit in the first state and the receiver qubit in the second state is ^^^^α etc. [0063]The count numbers ^^ and ^^ may be defined as the probability to obtain the first state and the second state of the receiver qubit respectively in case the sender state is in the first state. The probability may be modeled using the above equation of the transformed Bell state as follows: = tan ^. Hence, the rotation angle may
be obtained using the count numbers as follows: ^ =
[0064]Similarly, the count numbers ^^ and ^^ may be defined as the probability to obtain the first state and the second state of the receiver qubit respectively in case the sender state is in the second state. The probability may be modeled using the above equation of the transformed Bell state as follows: ^^ = ^^^^α or ^^ = ^^^^α. Hence, the rotation angle may be obtained using the count number as follows: α = sin^^ √^^ or α = cos^^ ^^^.
Claims
CLAIMS 1. A method of transmitting data from a sender quantum processing unit (103) to a receiver quantum processing unit (102), the method comprising: encoding (201) the data to be transmitted from the sender quantum processing unit to the receiver quantum processing unit, the encoding comprising mapping the data into a range of rotation angle values for obtaining a rotation angle encoding the data, receiving (202) a sign of the rotation angle by the receiver quantum processing unit; repeatedly performing: forming (203) a distributed entanglement state between a sender qubit in the sender quantum processing unit and a receiver qubit in the receiver quantum processing unit; and thereafter transforming (204) a qubit state of the sender qubit by the rotation angle; measuring (205) the sender qubit, resulting in a sender state of the sender qubit; receiving (206) by the receiver quantum processing unit the sender state; measuring (207) the receiver qubit, resulting in a receiver state of the receiver qubit; storing (208) a tuple of the sender state and the receiver state; calculating (210) by the receiver quantum processing unit the rotation angle using the sign of the rotation angle and the stored tuples of the sender and the receiver states, decoding the rotation angle for obtaining the data.
2. The method of claim 1, the calculation of the rotation angle comprising: selecting stored tuples which comprise a given state of the sender qubit, counting the number of measured first states of the receiver qubit and the number of measured second states of the receiver qubit from the selected tuples at the receiver quantum processing unit; using the counted numbers to calculate the rotation angle.
3. The method of claim 1, the calculation of the rotation angle comprising: a. for each distinct state of the sender qubit: i. selecting stored tuples which comprise the state of the sender qubit, ii. counting the number of measured first states of the receiver qubit and the number of measured second states of the receiver qubit from the selected tuples at the receiver quantum processing unit; iii. using the counted numbers to calculate an individual rotation angle; b. combining the individual rotation angles for calculating the rotation angle.
4. The method of any of the preceding claims, wherein the forming of the distributed entanglement state is performed at the sender quantum processing unit, the method further comprising receiving through a quantum channel the receiver qubit of the entanglement state by the receiver quantum processing unit.
5. The method of any of the preceding claims, wherein the encoding comprises: defining a unitary transformation representing one rotation operation of the qubit state of the sender qubit, the unitary transformation comprising trigonometric functions of the rotation angle.
6. The method of claim 5, the unitary transformation comprising a rotation matrix: ^cos ^
wherein α is the rotation angle. sin ^
7. The method of any of the preceding claims 1 to 6, wherein the range of ^ ^ rotation angle values lies between -90 degrees to +90 degrees (or - ^ to + radians).
8. The method of any of the preceding claims 5 to 7, wherein the distributed entanglement state is formed between the sender qubit and the receiver qubit and an additional sender qubit in an additional quantum processing unit, the method further comprising in each repetition: transforming a qubit state of the additional sender qubit by the rotation angle; measuring the additional sender qubit, resulting in a sender state of the additional sender qubit; receiving by the receiver quantum processing unit the sender state of the additional sender qubit; wherein the stored tuple further comprises the sender state of the additional sender qubit.
9. The method of claim 8, the calculation of the rotation angle comprising: selecting stored tuples which comprise a given state of the sender qubit and the additional sender qubit; counting the number of measured first states of the receiver qubit and the number of measured second states of the receiver qubit from the selected tuples at the receiver quantum processing unit; using the counted numbers to calculate the rotation angle.
10.The method of any of the preceding claims 2 to 9, further comprising normalizing the counted numbers, and using the normalized numbers to calculate the rotation angle.
11.The method of any preceding claims 1 to 10, wherein the sender and receiver qubits comprise two ion traps that enable the separation of the qubits by shooting.
12.The method of any preceding claims, wherein the sender and receiver qubits comprise superconducting qubits, semiconductor quantum dots, photonic qubits, defect-based qubits, topological nanowire qubits or nuclear magnetic resonance qubits.
13.The method of any of the preceding claims 1 to 12, wherein the mapping of the data is performed by applying a minmax scaler to the data.
14.A method of transmitting data from a sender quantum processing unit (103) to a receiver quantum processing unit (102), the method comprising at the sender quantum processing unit (103): encoding (201) the data to be transmitted from the sender quantum processing unit to the receiver quantum processing unit, the encoding comprising mapping the data into a range of rotation angle values for obtaining a rotation angle encoding the data, sending (202) a sign of the rotation angle to the receiver quantum processing unit; repeatedly performing: forming (203) a distributed entanglement state between a sender qubit in the sender quantum processing unit and a receiver qubit in the receiver quantum processing unit; and thereafter transforming (204) a qubit state of the sender qubit by the rotation angle; measuring (205) the sender qubit, resulting in a sender state of the sender qubit;
sending (206) the sender state to the receiver quantum processing unit. A method of transmitting data from a sender quantum processing unit (103) to a receiver quantum processing unit (102), the method comprising at the receiver quantum processing unit (102): receiving (202) a sign of a rotation angle by the receiver quantum processing unit, the rotation angle encoding the data; repeatedly performing: receiving (206) a sender state of a sender qubit in the sender quantum processing unit wherein the sender qubit is in a distributed entanglement state with a receiver qubit in the receiver quantum processing unit; measuring (207) the receiver qubit, resulting in a receiver state of the receiver qubit; storing (208) a tuple of the sender state and the receiver state; calculating (210) the rotation angle using the sign of the rotation angle and the stored tuples of the sender and the receiver states, decoding the rotation angle for obtaining the data by the receiver quantum processing unit. A quantum computing system (100) comprising a sender quantum processing unit (103) and a receiver quantum processing unit (102), wherein the sender quantum processing unit (103) is configured to perform the method of claim 14, wherein the receiver quantum processing unit (102) is configured to perform the method claim 15. The method of any of the preceding claims 1 to 15, the data comprising any one of: a number, a certificate, a key, a token, a public key and a private key.
The method of any of the preceding claims 1 to 15, comprising a migration method for migrating from a first Hardware Security Module, HSM, to a second HSM, wherein the first HSM is associated with a first asymmetrical cryptographic key pair having a first personal key and a first public key and a first certificate containing the first public key, wherein the migration method comprises the following steps: generating a second asymmetrical cryptographic key pair having a second personal key and a second public key and a second certificate, which contains the second public key, by the second HSM, transmitting the second certificate with the second public key from the second HSM to the first HSM, and generating a third certificate by the first HSM by signing the second public key using the first personal key, wherein a certificate check of the second certificate can be carried out by way of a certificate chain containing the first and third certificates, wherein the transmitting of the second certificate comprises the transmission of the data, wherein the data comprises the second certificate.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102023118865.8A DE102023118865A1 (en) | 2023-07-17 | 2023-07-17 | QUANTUM COMMUNICATION OF DATA USING A DISTRIBUTED ENTANGLEMENT STATE |
| PCT/EP2024/069710 WO2025016878A1 (en) | 2023-07-17 | 2024-07-11 | Quantum communication of data using a distributed entanglement state |
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| EP1919122A1 (en) | 2006-10-31 | 2008-05-07 | British Telecommunications Public Limited Company | Quantum communication method and system between two user using two pairs of photons emitted by an independent laser source |
| WO2011006912A1 (en) | 2009-07-15 | 2011-01-20 | Bundesdruckerei Gmbh | Method for hsm migration |
| GB201402599D0 (en) * | 2014-02-14 | 2014-04-02 | Univ Edinburgh | Client server communication system |
| EP4053756A1 (en) * | 2021-03-02 | 2022-09-07 | Cambridge Quantum Computing Limited | Quantum computing system and method |
| US11516190B1 (en) * | 2021-08-26 | 2022-11-29 | Accenture Global Solutions Limited | Secret superposition protocols for quantum computation |
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