A quantum communications system may include a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may include a pulse transmitter, a pulse divider downstream from the pulse transmitter, and at least one first waveplate upstream from the pulse divider and configured to alter a polarization state of pulses travelling therethrough. The receiver node may include at least one second waveplate being a conjugate of the at least one first waveplate, a pulse recombiner upstream from the at least one second waveplate, and a pulse receiver downstream from the at least one second waveplate.

The disclosure describes aspects of using multiple species in trapped-ion nodes for quantum networking. In an aspect, a quantum networking node is described that includes multiple memory qubits, each memory qubit being based on a .sup.171Yb.sup.+ atomic ion, and one or more communication qubits, each communication qubit being based on a .sup.138Ba.sup.+ atomic ion. The memory and communication qubits are part of a lattice in an atomic ion trap. In another aspect, a quantum computing system having a modular optical architecture is described that includes multiple quantum networking nodes, each quantum networking node including multiple memory qubits (e.g., based on a .sup.171Yb.sup.+ atomic ion) and one or more communication qubits (e.g., based on a .sup.138Ba.sup.+ atomic ion). The memory and communication qubits are part of a lattice in an atomic ion trap. The system further includes a photonic entangler coupled to each of the multiple quantum networking nodes.

A quantum-computing threats surveillance system for use in quantum communication environments is a quantum-surveillance technology which detects quantum computing threats based on free electron monitoring and entangled state measurement, and performs time-and-space analysis on quantum communication environments via making use of specific Fourier transforms, and then collaborate with a system of Lotka-Volterra competition models for variance analysis, so as to determine whether there is suspicious or potential quantum computing in a quantum communication environment. Furthermore, it can monitor different quantum-teleportation channels to achieve the effect of tracking specific quantum-computing behaviors for a long term.

An example operation may include one or more of receiving a location of an output stored on a data structure of a blockchain, where the location comprises a path of hashes generated by a reduced-step hash instead of a full-step hash of the blockchain, performing an approximate hash verification on the path of hashes based on the reduced-step hash values to verify whether the output is unused, and in response to a determination that the output is unused as a result of the approximate hash verification, approving a use of the output by a client associated with the output.

Entangled quantum photons augment a classically encrypted data message and the augmented message, classical decryption key and quantum photon augmentation key are transmitted on a single classical transmission line to a receiver. Eavesdroppers, i.e., attacks, are detected in accordance with changes to the quantum photons in the augmented message.

A method comprising generating an updated security key upon expiration of a key exchange timer, transferring the updated security key to a Coaxial Network Unit (CNU), retaining an original key, wherein the updated security key comprises a different key identification number than the original key, accepting and decrypting upstream traffic that employs either the original key or the updated key, after transferring the updated security key to the CNU, creating a key switchover timer, before the key switchover timer expires, verify that upstream traffic transferred from the CNU on a logical link uses the updated security key, and when upstream traffic is encrypted using the updated security key, begin using the updated security key to encrypt downstream traffic and clear the key switchover timer.

A system and method for establishing and using quantum safe enclaves is described. In some embodiments, secure shared randomness is distributed between nodes, for example using quantum key distribution. The secured shared randomness is used to generate quantum safe network keys that enable quantum safe network links to be established between any of the nodes included in the quantum safe enclave. A network manager enforces policies that restrict communications between nodes of the quantum safe enclave to transmission via quantum safe network links. Such an arrangement protects communicated data from quantum enabled attacks that may compromise other forms of encryption.

A method of communicating a classical message M between a first party A and a second distant party B over a public channel F, comprises the steps of sharing a key between the parties, the shared key K comprising a short-term-secure key KS and/or a long-term-secure key KL; at A, encoding M as a quantum codeword, A using K to encode M into a first encrypted codeword belonging to a publicly known quantum code; communicating the first encrypted codeword from A to B over F whose output is a second codeword; unitarily transforming the second codeword into a third codeword by using a N-mode interferometer controlled by B, placed at the output of F and keyed by K; determining an estimate of M, at B, by performing a measurement on the third codeword and by processing the measurement using K.

According to an embodiment, a quantum communication device is adapted to correct first sift key data acquired by performing sift processing with respect to a quantum bit string received from a transmission device via a quantum communication path. The quantum communication device includes a determination unit and a correction unit. The determination unit determines setting information of error correction on the first sift key data from an estimated error rate of the first sift key data and a margin of the estimated error rate. The correction unit generates corrected key data by performing the error correction with the setting information.

The disclosed technology includes a technique for securing communications over a wireless telecommunications network. Quantum entangled particles are generated and optically communicated to a wireless endpoint device (e.g., smartphone) within Line-of-Sight (LOS) of the particle generator and optionally to a network access node (e.g., base station). A particle generator can be positioned on a communications tower, mountain, tall building, or other structure that enables greater LOS to multiple endpoint devices and network access nodes. The quantum states of entangled particles are used to generate counterpart cryptographic keys at the wireless endpoint device and network access node. As such, the counterpart keys can secure communications while underlying particles remain quantumly entangled. Moreover, any third-party observation of a quantumly entangled particle would cause collapse of the entanglement, which would render the cryptographic keys inoperable and serve to alert the network that an entangled particle was compromised.