Merge pull request #141 from quantumlib/measurements

Add measurement gate.

apps/qsim_amplitudes.cc

@@ -33,13 +33,15 @@
 
 constexpr char usage[] = "usage:\n  ./qsim_amplitudes -c circuit_file "
                          "-d times_to_save_results -i input_files "
-                         "-o output_files -t num_threads -v verbosity\n";
+                         "-o output_files -s seed -t num_threads "
+                         "-v verbosity\n";
 
 struct Options {
   std::string circuit_file;
   std::vector<unsigned> times = {std::numeric_limits<unsigned>::max()};
   std::vector<std::string> input_files;
   std::vector<std::string> output_files;
+  unsigned seed = 1;
   unsigned num_threads = 1;
   unsigned verbosity = 0;
 };
@@ -53,7 +55,7 @@ Options GetOptions(int argc, char* argv[]) {
     return std::atoi(word.c_str());
   };
 
-  while ((k = getopt(argc, argv, "c:d:i:o:t:v:")) != -1) {
+  while ((k = getopt(argc, argv, "c:d:i:s:o:t:v:")) != -1) {
     switch (k) {
       case 'c':
         opt.circuit_file = optarg;
@@ -67,6 +69,9 @@ Options GetOptions(int argc, char* argv[]) {
       case 'o':
         qsim::SplitString(optarg, ',', opt.output_files);
         break;
+      case 's':
+        opt.seed = std::atoi(optarg);
+        break;
       case 't':
         opt.num_threads = std::atoi(optarg);
         break;
@@ -167,9 +172,10 @@ int main(int argc, char* argv[]) {
     }
   };
 
-  using Runner = QSimRunner<IO, BasicGateFuser<GateQSim<float>>, Simulator>;
+  using Runner = QSimRunner<IO, BasicGateFuser<IO, GateQSim<float>>, Simulator>;
 
   Runner::Parameter param;
+  param.seed = opt.seed;
   param.num_threads = opt.num_threads;
   param.verbosity = opt.verbosity;
   Runner::Run(param, opt.times, circuit, measure);

apps/qsim_base.cc

@@ -30,26 +30,30 @@
 struct Options {
   std::string circuit_file;
   unsigned maxtime = std::numeric_limits<unsigned>::max();
+  unsigned seed = 1;
   unsigned num_threads = 1;
   unsigned verbosity = 0;
 };
 
 Options GetOptions(int argc, char* argv[]) {
   constexpr char usage[] = "usage:\n  ./qsim_base -c circuit -d maxtime "
-                           "-t threads -v verbosity\n";
+                           "-s seed -t threads -v verbosity\n";
 
   Options opt;
 
   int k;
 
-  while ((k = getopt(argc, argv, "c:d:t:v:")) != -1) {
+  while ((k = getopt(argc, argv, "c:d:s:t:v:")) != -1) {
     switch (k) {
       case 'c':
         opt.circuit_file = optarg;
         break;
       case 'd':
         opt.maxtime = std::atoi(optarg);
         break;
+      case 's':
+        opt.seed = std::atoi(optarg);
+        break;
       case 't':
         opt.num_threads = std::atoi(optarg);
         break;
@@ -81,7 +85,7 @@ void PrintAmplitudes(
     "000", "001", "010", "011", "100", "101", "110", "111",
   };
 
-  uint64_t size = std::min(uint64_t{8}, state_space.Size(state));
+  uint64_t size = std::min(uint64_t{8}, state_space.Size());
   unsigned s = 3 - std::min(unsigned{3}, num_qubits);
 
   for (uint64_t i = 0; i < size; ++i) {
@@ -108,7 +112,7 @@ int main(int argc, char* argv[]) {
   using Simulator = qsim::Simulator<For>;
   using StateSpace = Simulator::StateSpace;
   using State = StateSpace::State;
-  using Runner = QSimRunner<IO, BasicGateFuser<GateQSim<float>>, Simulator>;
+  using Runner = QSimRunner<IO, BasicGateFuser<IO, GateQSim<float>>, Simulator>;
 
   StateSpace state_space(circuit.num_qubits, opt.num_threads);
   State state = state_space.CreateState();
@@ -121,6 +125,7 @@ int main(int argc, char* argv[]) {
   state_space.SetStateZero(state);
 
   Runner::Parameter param;
+  param.seed = opt.seed;
   param.num_threads = opt.num_threads;
   param.verbosity = opt.verbosity;
 

apps/qsim_von_neumann.cc

@@ -32,26 +32,30 @@
 struct Options {
   std::string circuit_file;
   unsigned maxtime = std::numeric_limits<unsigned>::max();
+  unsigned seed = 1;
   unsigned num_threads = 1;
   unsigned verbosity = 0;
 };
 
 Options GetOptions(int argc, char* argv[]) {
   constexpr char usage[] = "usage:\n  ./qsim_von_neumann -c circuit -d maxtime "
-                           "-t threads -v verbosity\n";
+                           "-s seed -t threads -v verbosity\n";
 
   Options opt;
 
   int k;
 
-  while ((k = getopt(argc, argv, "c:d:t:v:")) != -1) {
+  while ((k = getopt(argc, argv, "c:d:s:t:v:")) != -1) {
     switch (k) {
       case 'c':
         opt.circuit_file = optarg;
         break;
       case 'd':
         opt.maxtime = std::atoi(optarg);
         break;
+      case 's':
+        opt.seed = std::atoi(optarg);
+        break;
       case 't':
         opt.num_threads = std::atoi(optarg);
         break;
@@ -104,15 +108,15 @@ int main(int argc, char* argv[]) {
       return p != 0 ? p * std::log(p) : 0;
     };
 
-    auto size = state_space.Size(state);
-    double entropy = -For::RunReduce(opt.num_threads, size, f, Op(),
-                                     state_space, state);
+    double entropy = -For::RunReduce(opt.num_threads, state_space.Size(), f,
+                                     Op(), state_space, state);
     IO::messagef("entropy=%g\n", entropy);
   };
 
-  using Runner = QSimRunner<IO, BasicGateFuser<GateQSim<float>>, Simulator>;
+  using Runner = QSimRunner<IO, BasicGateFuser<IO, GateQSim<float>>, Simulator>;
 
   Runner::Parameter param;
+  param.seed = opt.seed;
   param.num_threads = opt.num_threads;
   param.verbosity = opt.verbosity;
 

docs/input_format.md

@@ -41,3 +41,7 @@ fSim(θ, φ)                                              | time fs qubi
 CPhase(φ)                                                     | time cp qubit1 qubit2 phi       | 6 cp 0 1 0.78
 Identity (1-qubit)                                                | time id1 qubit                  | 7 id1 0
 Identity (2-qubit)                                                | time id2 qubit                  | 8 id2 0 1
+Measurement (n-qubit)                                             | time m qubit1 qubit2 ...        | 9 m 0 1 2 3
+
+Gate times should be ordered. Measurement gates with equal times get fused
+together.

lib/BUILD

@@ -207,7 +207,10 @@ cc_library(
 cc_library(
     name = "fuser_basic",
     hdrs = ["fuser_basic.h"],
-    deps = [":fuser"],
+    deps = [
+        ":fuser",
+        ":gate",
+    ],
 )
 
 ### Helper libraries to run qsim and qsimh ###
@@ -216,6 +219,7 @@ cc_library(
     name = "run_qsim",
     hdrs = ["run_qsim.h"],
     deps = [
+        ":gate",
         ":gate_appl",
         ":util",
     ],
@@ -235,6 +239,7 @@ cc_library(
 cc_library(
     name = "statespace",
     hdrs = ["statespace.h"],
+    deps = [":util"],
 )
 
 cc_library(

lib/circuit_qsim_parser.h

@@ -169,6 +169,21 @@ class CircuitQsimParser final {
           ss >> q0 >> q1 >> phi;
           if (!ValidateGate(ss, num_qubits, q0, q1, provider, k)) return false;
           gates.push_back(GateCP<fp_type>::Create(time, q0, q1, phi));
+        } else if (gate_name == "m") {
+          std::vector<unsigned> qubits;
+          qubits.reserve(num_qubits);
+          do {
+            ss >> q0;
+            if (ss) {
+              qubits.push_back(q0);
+            } else {
+              InvalidGateError(provider, k);
+              return false;
+            }
+          } while (ss.peek() != std::stringstream::traits_type::eof());
+          if (!ValidateGate(ss, num_qubits, qubits, provider, k)) return false;
+          gates.push_back(gate::Measurement<GateQSim<fp_type>>::Create(
+              time, std::move(qubits)));
         } else {
           InvalidGateError(provider, k);
           return false;
@@ -247,6 +262,27 @@ class CircuitQsimParser final {
 
     return true;
   }
+
+  /**
+   * Checks formatting for a multiqubit gate parsed from 'ss'.
+   * @param ss Input stream containing the gate specification.
+   * @param num_qubits Number of qubits, as defined at the start of the file.
+   * @param qubits Indices of affected qubits.
+   * @param provider Circuit source; only used for error reporting.
+   * @param line Line number of the parsed gate; only used for error reporting.
+   */
+  static bool ValidateGate(std::stringstream& ss, unsigned num_qubits,
+                           const std::vector<unsigned>& qubits,
+                           const std::string& provider, unsigned line) {
+    for (auto q : qubits) {
+      if (q >= num_qubits) {
+        InvalidGateError(provider, line);
+        return false;
+      }
+    }
+
+    return true;
+  }
 };
 
 }  // namespace qsim

lib/fuser.h

@@ -24,7 +24,7 @@ struct GateFused {
   typename Gate::GateKind kind;  // Kind of the (first) master gate.
   unsigned time;
   unsigned num_qubits;
-  unsigned qubits[3];
+  std::vector<unsigned> qubits;
   const Gate* pmaster;
   std::vector<const Gate*> gates;
 };