Enhancing security of quantum communication channels
Methods, apparatus, and computer program products for quantum communications and quantum information processing are provided. An example method includes determining a received state of a qubit received via a quantum communication link where the received state includes one or more properties of the received qubit. The method further accesses a transmitted state of the qubit where the transmitted state includes one or more properties of the qubit as transmitted. The method continues by comparing the one or more properties of the qubit in the received state with the one or more properties of the qubit in the transmitted state. Finally, the method detects a condition of the quantum communication link based on the comparison between the received state and the transmitted state. In doing so, the embodiments operate to characterize the noise level, security, etc. of a quantum communication interconnect, link, or channel.
1 . A quantum communication method comprising:
determining a received state of a qubit received via a quantum communication link, wherein the received state of the qubit comprises one or more properties of the received qubit;
accessing a transmitted state of the qubit, wherein the transmitted state of the qubit comprises one or more properties of the qubit as transmitted;
comparing the one or more properties of the received qubit with the one or more properties of the qubit as transmitted;
determining a first spatial location associated with the received state of the qubit;
accessing a second spatial location associated with the transmitted state of the qubit;
determining a displacement between the first spatial location and the second spatial location; and
detecting a condition of the quantum communication link based on the displacement between the first spatial location and the second spatial location.
2 . The method according to claim 1 , further comprising detecting an eavesdropper device accessing the quantum communication link based on the comparison between the one or more properties of the received qubit and the one or more properties of the qubit as transmitted.
3 . The method according to claim 2 , wherein the eavesdropper device accessing the quantum communication link utilizes weak measurements.
4 . The method according to claim 1 , wherein:
the one or more properties of the received qubit comprise at least a position associated with the received qubit, and
the one or more properties of the qubit as transmitted comprise at least a position associated with the qubit as transmitted, wherein
detecting the condition of the quantum communication link further comprises:
measuring the position associated with the received qubit; and
comparing the position associated with the received qubit with the position associated with the qubit as transmitted.
5 . The method according to claim 4 , wherein measuring the position associated with the received qubit comprises measuring the first spatial location associated with the received state of the qubit.
6 . The method according to claim 5 , wherein the first spatial location associated with the received state of the qubit is measured via an imaging device.
7 . The method according to claim 1 , further comprising determining a received encoded value based at least in part on the one or more properties of the received qubit, wherein the received encoded value is communicated by the transmission of a single photon.
8 . The method according to claim 5 , wherein measuring the position associated with the received qubit comprises measuring a time of arrival of the received qubit.
9 . The method according to claim 8 , wherein detecting the condition of the quantum communication link further comprises:
accessing a time of transmittal associated with the qubit as transmitted;
determining a travel time between the time of transmittal associated with the qubit as transmitted qubit and the time of arrival of the received qubit; and
detecting the condition of the quantum communication link based on the travel time.
10 . The method according to claim 1 , wherein a plurality of qubits are received, and each qubit of the plurality of qubits comprises a single photon of an entangled pair.
11 . The method according to claim 10 , further comprising:
transmitting a subset of the received plurality of qubits to a transmit module associated with the transmitted state of the qubit.
12 . The method according to claim 1 , wherein a plurality of qubits are received, each of the plurality of received qubits having a transmitted encoded value according to a transmitted basis vector, the method further comprising:
determining, for each of the plurality of received qubits, a corresponding received encoded value based at least in part on one or more corresponding properties of the received qubit of the plurality;
comparing, for a subset of the plurality of received qubits, the received encoded value with the transmitted encoded value; and
detecting the condition of the quantum communication link based on the comparison, for the subset of the plurality of received qubits, of the received encoded value and the transmitted encoded value,
wherein the subset of the plurality of received qubits comprises received encoded values corresponding to a basis vector that matches the transmitted basis vector and wherein the subset of the plurality of received qubits further comprises received encoded values corresponding to a basis vector that fails to match the transmitted basis vector.
13 . The method according to claim 1 , wherein the first spatial location associated with the received state of the qubit comprises a physical position of the qubit in the cross-section of a transmitting medium.
14 . A computer program product for quantum communications, the computer program product comprising at least one non-transitory computer-readable storage medium storing program instructions that, when executed, cause the computer program product to:
determine a received state of a qubit received via a quantum communication link, wherein the received state of the qubit comprises one or more properties of the received qubit;
access a transmitted state of the qubit, wherein the transmitted state of the qubit comprises one or more properties of the qubit as transmitted;
compare the one or more properties of the received qubit with the one or more properties of the qubit as transmitted;
determine a first spatial location associated with the received state of the qubit;
access a second spatial location associated with the transmitted state of the qubit;
determine a displacement between the first spatial location and the second spatial location; and
detect a condition of the quantum communication link based on the displacement between the first spatial location and the second spatial location.
15 . The computer program product according to claim 14 , further comprising program instructions that, when executed, cause the computer program product to detect an eavesdropper device accessing the quantum communication link based on the comparison between the one or more properties of the received qubit and the one or more properties of the qubit as transmitted.
16 . The computer program product according to claim 15 , wherein the eavesdropper device accessing the quantum communication link utilizes weak measurements.
17 . The computer program product according to claim 14 , wherein:
the one or more properties of the received qubit comprise at least a position associated with the received qubit, and
the one or more properties of the qubit as transmitted comprise at least a position associated with the qubit as transmitted, the computer program product further comprising program instructions that, when executed, cause the computer program product to detect the condition of the quantum communication link by:
measuring the position associated with the received qubit; and
comparing the position associated with the received qubit with the position associated with the qubit as transmitted.
18 . The computer program product according to claim 17 , further comprising program instructions that, when executed, cause the computer program product to measure the position associated with the received qubit by measuring the first spatial location associated with the received state of the qubit.
19 . The computer program product according to claim 18 , wherein the first spatial location associated with the received state of the qubit is measured using an imaging device.
20 . The computer program product according to claim 14 , further comprising program instructions that, when executed, cause the computer program product to:
determine a received encoded value based at least in part on the one or more properties of the received qubit, wherein the received encoded value is communicated by the transmission of a single photon.
21 . The computer program product according to claim 17 , further comprising program instructions that, when executed, cause the computer program product to:
measure the position associated with the received qubit by measuring a time of arrival of the received qubit.
22 . The computer program product according to claim 21 , further comprising program instructions that, when executed, cause the computer program product to detect the condition of the quantum communication link by:
determining the time of arrival of the received state of the qubit;
accessing a time of transmittal associated with the qubit as transmitted;
determining a travel time between the time of transmittal associated with the qubit as transmitted and the time of arrival of the received qubit; and
detecting the condition of the quantum communication link based on the travel time.
23 . The computer program product according to claim 14 , wherein a plurality of qubits are received, and each qubit of the plurality of qubits comprises a single photon of an entangled pair.
24 . The computer program product according to claim 23 , further comprising program instructions that, when executed, cause the computer program product to transmit a subset of the received plurality of qubits to a transmit module associated with the transmitted state of the qubit.
25 . The computer program product according to claim 14 , wherein
a plurality of qubits are received, each of the plurality of received qubits having a transmitted encoded value according to a transmitted basis vector, the computer program product further comprising program instructions that, when executed, cause the computer program product to:
determine, for each of the plurality of received qubits, a corresponding received encoded value based at least in part on one or more properties of the received qubit of the plurality;
compare, for a subset of the plurality of received qubits, the received encoded value with the transmitted encoded value; and
detect a condition of the quantum communication link based on the comparison, for the subset of the plurality of received qubits, of the received encoded value and the transmitted encoded value,
wherein the subset of the plurality of received qubits comprises received encoded values corresponding to a basis vector that matches the transmitted basis vector and wherein the subset of the plurality of received qubits further comprises received encoded values corresponding to a basis vector that fails to match the transmitted basis vector.
26 . The computer program product according to claim 14 , wherein the first spatial location associated with the received state of the qubit comprises a physical position of the qubit in the cross-section of a transmitting medium.